EgDf1 is a developmentally regulated protein from the parasite Echinococcus granulosus related to... more EgDf1 is a developmentally regulated protein from the parasite Echinococcus granulosus related to a family of hydrophobic ligand binding proteins. This protein could play a crucial role during the parasite life cycle development since this organism is unable to synthetize most of their own lipids de novo. Furthermore, it has been shown that two related protein from other parasitic platyhelminths (Fh15 from Fasciola hepatica and Sm14 from Schistosoma mansoni) are able to confer protective inmunity against experimental infection in animal models. A three-dimensional structure would help establishing structure/function relationships on a knowledge based manner. 3D structures for EgDf1 protein were modelled by using myelin P2 (mP2) and intestine fatty acid binding protein (I-FABP) as templates. Molecular dynamics techniques were used to validate the models. Template mP2 yielded the best 3D structure for EgDf1. Palmitic and oleic acids were docked inside EgDf1. The present theoretical re...
Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extr... more Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extracts were prepared for analysis of DNA-protein interactions involving specific transcriptional regulatory factors. Gel mobility-shift assays were done using a heterologous probe containing binding sites for widespread transcription factors. A fragment of the promoter of GATA-1 transcription factor from the chicken was selected. When nuclear extracts from E. granulosus protoscolices were assayed a specific band shift was observed. The methodologies developed in this study could provide an important contribution for the characterization of the DNA-protein interactions involved in transcriptional regulation within the context of recent developments in the molecular biology of this parasite.
Fatty acid-binding proteins (FABPs) are candidate molecules for vaccines against several parasiti... more Fatty acid-binding proteins (FABPs) are candidate molecules for vaccines against several parasitic platyhelminths. A FABP from the cestode Echinococcus granulosus (EgDf1) was expressed in Salmonella vaccine strains as a C-terminal fusion to fragment C of tetanus toxin (TetC) by using expression vector pTECH. The fusion protein was equally expressed in several attenuated vaccine strains derived from bacteria with different genetic backgrounds and different attenuating mutations. Single-dose immunization experiments with the aroA Salmonella typhimurium strain SL3261 carrying the pTECH-EgDf1 construct were conducted with mice, using both the intravenous and the oral routes. Surprisingly, the antibody response to EgDf1 and the antigen-specific cytokine production in spleen cells were stronger in mice immunized orally. Furthermore, immune mouse sera strongly reacted with fixed sections of the worm's larval stage. Analysis of the isotype distribution of the specific anti-EgDf1 antibod...
We report the isolation of a differentially expressed gene, EgTrp, which is expressed in the prot... more We report the isolation of a differentially expressed gene, EgTrp, which is expressed in the protoscoleces (PS) of Echinococcus granulosus. The experimental design was based on a differential immuno-screening of a PS kgt11 cDNA library. We used antisera raised against PS and against germinal layers, selecting those clones exclusively reactive against the former antiserum. The insert of one of the
A number of silent codon changes were made in two Escherichia coli genes. For the ompA gene, the ... more A number of silent codon changes were made in two Escherichia coli genes. For the ompA gene, the replacement of seven consecutive frequently used codons with synonymous infrequently used codons reduced the ompA mRNA level and its half-life. For the bla gene, the exchange of 24 codons for the most frequently used synonymous codons extended the bla mRNA half-life. A modification of ribosome traffic could account for these observations.
Transcription initiation from beta-lactamase, tetracycline resistance and RNA 1 promoters, presen... more Transcription initiation from beta-lactamase, tetracycline resistance and RNA 1 promoters, present in plasmid pAT153, were studied employing the abortive initiation technique. Assays appear to be promoter-specific with supercoiled and linear templates. Supercoiling enhances the isomerization rate constant of the open RNA-polymerase--promoter complex formation. Results agree with the in vivo behaviour of the corresponding promoters, and allow us to propose a hypothesis about the effect of supercoiling on transcription initiation.
The interaction between E. coli RNA polymerase and the tetR promoter from pSC101, was studied by ... more The interaction between E. coli RNA polymerase and the tetR promoter from pSC101, was studied by protection and premodification experiments, using dimethyl sulfate, methylation of single stranded cytosines, and DNAase I footprinting. Whereas qualitative and quantitative results from the chemical approach conform to patterns already displayed by other promoter systems, hypersensitive sites to DNAase I attack differ from those of other promoters. Distribution and nature of the contacts suggest that regions of the promoter sequence participates differently in complex formation. The involvement of major and minor grooves of the double helix in the complex with the enzyme, differs along the promoter. After a comparison of the results from seven different promoters, a pattern of conserved contacts seem to appear. Comparison of temperature dependence of local unwinding around the transcription start site (detected by the appearance of single stranded cytosines), and DNAase I footprinting, reveals that the process leading to stable complex formation can be achieved without disruption of base-pairing.
Two synthetic DNA sequences, carrying no other known E. coli promoter element than the consensus ... more Two synthetic DNA sequences, carrying no other known E. coli promoter element than the consensus hexamers (CH) TTGACA (CH-35) and TATAAT CH(-10), spaced by 17 bp, were inserted in pBR329, in a position enabling transcription of the complete Cmr gene. The region upstream of the Cmr transcription start was carefully cleared of w.t. promoter elements (full deletion of the wild type (w.t.) Cmr promoter upstream +2 and large portion of an upstream coding sequence). Both synthetic promoters, which differ only by the sequences of the spacers (non consensus, constrained in AT or GC) support in vivo high level Cmr gene expression. The GC rich spacer is associated with transcription start at the usual +1 position, but with the AT rich spacer, transcription starts at several places, mainly in CH(-10). Rearranged promoter sequences derived from the synthetic ones upon transformation with partly ligated plasmids, yield new insights on the role of the standard CH pair, the size of the spacer and the sequence downstream of CH(-10).
A relatively important change in UV absorption is observed upon thermal perturbation of nucleotid... more A relatively important change in UV absorption is observed upon thermal perturbation of nucleotide solutions. Comparison of these thermal perturbation spectra of nucleic acid residues with solvent perturbation spectra of the same compounds suggests that this spectral change can most probably be attributed to temperature induced hydration change of the bases. This conclusion is confirmed by the results obtained from acid-base perturbation spectra of these nucleotides as well as thermal perturbation spectra of nucleotides containing modified bases. It is shown that this temperature dependent change in UV absorption is also present in dinucleoside monophosphates. In that case, this effect is superimposed upon the well known change in absorbance due to the unstacking of the bases during heating.
The structure of the final initiation complex between E. coli RNA polymerase (RNAP) and the bla p... more The structure of the final initiation complex between E. coli RNA polymerase (RNAP) and the bla promoter from the transposon TN3 has been probed by footprinting experiments and base accessibility to dimethyl sulfate at 37 degrees C. At RNAP/promoter molar ratios "standard" for these experiments (greater than or equal to 10), the contacts on bla extend from -100 to +20, i.e. a length exceeding twice the dimension of the RNAP major axis [33]. Since footprinting at about equimolar amounts of RNAP and bla extends to the usual (-55 to +20) promoter domain, it is very likely that at least two RNAP's participate in the complex observed at tenfold higher RNAP/bla ratios. Under the latter conditions, the extended footprint (-100 to +20) is observed above 30 degrees C, whereas at 15 degrees C, only the -55 to +20 promoter area is contacted. Furthermore, gel retardation experiments show the presence of two complexes of different migration rates. We have reported earlier [21] that at the "standard" RNAP/bla ratio, transcription initiation from the bla promoter is inhibited. The correlation of this inhibition with the postulated two RNAP/bla complex suggests a regulation of bla gene expression by RNAP availability controlled for instance by growth rate. These results can be correlated with those reported in [14, 15] for the tyrT promoter. Interestingly, both promoter share significant sequence homologies.
We showed earlier that the region of the bla promoter of Tn3 protected by the RNA-polymerase (RNA... more We showed earlier that the region of the bla promoter of Tn3 protected by the RNA-polymerase (RNAP), has the normal size (about 60bp) at RNAP/promoter molar ratio r less than or equal to 2, but rises to about twice this extent as r increases. We confirm here that the species corresponding to normal and extended footprint distinguish by their electrophoretic mobilities. Furthermore, inspection of the complexes by electron microscopy confirms that at r greater than 2, the bla promoter can bind specifically a second RNAP particle, as compared to the 1:1 complex observed at r less than or equal to 2. At r greater than 2, the ability of the bla promoter to initiate transcription in vitro is repressed when compared to the complex 1:1 obtained at r less than or equal to 2. The unexpected decrease in initiation efficiency as the concentration of RNAP particles is increased, together with the striking sequence homology of the bla promoter with promoters of stable RNA, suggest that in vivo, this promoter could be regulated by growth rate.
1. Mol Biochem Parasitol. 1993 Jun;59(2):335-8. Isolation and characterization of a middle repeti... more 1. Mol Biochem Parasitol. 1993 Jun;59(2):335-8. Isolation and characterization of a middle repetitive DNA element from Echinococcus granulosus. Marín M, Garat B, Pettersson U, Ehrlich R. Departamento de Bioquímica, Facultad de Ciencias, Montevideo, Uruguay. ...
In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloni... more In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloning strategy was developed. Degenerate oligonucleotides were designed for the most conserved sequence in GATA proteins that include 20 amino acids of the zinc domain. A 60 bp fragment was isolated that had high homology among this sequence and those reported in other species. An analogous sequence was obtained by performing the same procedure with DNA from the free living platyhelminth Dugesia tigrina. High stringency Southern blotting experiments confirmed the presence of this sequence in the parasite genome.
Echinococcus granulosus is the causative agent of hydatidosis, a major zoonoses that affects huma... more Echinococcus granulosus is the causative agent of hydatidosis, a major zoonoses that affects humans and herbivorous domestic animals. The disease is caused by the pressure exerted on viscera by hydatid cysts that are formed upon ingestion of E. granulosus eggs excreted by canine. Protoscoleces, larval forms infective to canine, develop asynchronously and clonally from the germinal layer (GL) of hydatid cysts. In this report, we describe the cellular organization and the appearance of differentiated structures both in nascent buds and developed protoscoleces attached to the GL. Early protoscolex morphogenesis is a highly complex and dynamic process starting from the constitution of a foramen in the early bud, around which nuclei are distributed mainly at the lateral and apical regions. Similarly, distribution of nuclei in mature protoscoleces is not homogenous but underlies three cellular territories: the suckers, the rostellar pad, and the body, that surrounds the foramen. Several nuclei are associated to calcareous corpuscles (Cc), differentiated structures that are absent in the earlier bud stages. The number of nuclei is similar from the grown, elongated bud stage to the mature protoscolex attached to the GL, strongly suggesting that there is no significant cellular proliferation during final protoscolex development. The amount of DNA per nucleus is in the same range to the one described for most other platyhelminthes. Our results point to a sequential series of events involving cell proliferation, spatial cell organization, and differentiation, starting in early buds at the GL of fertile hydatid cysts leading to mature protoscoleces infective to canine.
In this paper we examine a new distance-based method for identifying and characterizing possible ... more In this paper we examine a new distance-based method for identifying and characterizing possible interactions between biological structures and objects, with respect to the initial developmental stages of Echinococcus granulosus. By adopting the surface of the foramen as the distance reference, several interesting results have been identified, including the fact that the cell nuclei tend to be organized with respect to the foramen surface as well as the stability of the spatial distribution of these nuclei along the development stages.
Four fatty acid binding proteins (FABPs) have been described in 4 parasitic platyhelminths: Schis... more Four fatty acid binding proteins (FABPs) have been described in 4 parasitic platyhelminths: Schistosoma mansoni, Schistosoma japonicum, Fasciola hepatica and Echinococcus granulosus. FABPs form a multigenic family of cytosolic proteins widely distributed in metazoan tissues, the function of which is still poorly understood. These helminth proteins have recently received attention, since there are reports to indicate that S. mansoni and F. hepatica FABPs may be protective antigens. In addition, these proteins could play a major role in the parasites' life-cycles because platyhelminths are unable to synthesize de novo most of their lipids. We have undertaken phylogenetic and structural analyses of platyhelminth FABPs in an attempt to characterize features of biological relevance. Phylogenetically, these FABPs appear to be more closely related to those of vertebrate heart, mammary gland, muscle, retina, skin, brain and myelin, although no clear functional relationships were established between them. We describe several conserved motifs characteristic of specific groups of FABPs. Hydrophilicity, flexibility and accessibility analyses revealed several major putative epitopes for the E. granulosus FABP, EgDf1, that appear to be centred in loops of the EgDf1 3-dimensional structure modelled by molecular replacement.
EgDf1 is a developmentally regulated protein from the parasite Echinococcus granulosus related to... more EgDf1 is a developmentally regulated protein from the parasite Echinococcus granulosus related to a family of hydrophobic ligand binding proteins. This protein could play a crucial role during the parasite life cycle development since this organism is unable to synthetize most of their own lipids de novo. Furthermore, it has been shown that two related protein from other parasitic platyhelminths (Fh15 from Fasciola hepatica and Sm14 from Schistosoma mansoni) are able to confer protective inmunity against experimental infection in animal models. A three-dimensional structure would help establishing structure/function relationships on a knowledge based manner. 3D structures for EgDf1 protein were modelled by using myelin P2 (mP2) and intestine fatty acid binding protein (I-FABP) as templates. Molecular dynamics techniques were used to validate the models. Template mP2 yielded the best 3D structure for EgDf1. Palmitic and oleic acids were docked inside EgDf1. The present theoretical re...
Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extr... more Nuclei from Echinococcus granulosus protoscolices were isolated from infected sheep. Protein extracts were prepared for analysis of DNA-protein interactions involving specific transcriptional regulatory factors. Gel mobility-shift assays were done using a heterologous probe containing binding sites for widespread transcription factors. A fragment of the promoter of GATA-1 transcription factor from the chicken was selected. When nuclear extracts from E. granulosus protoscolices were assayed a specific band shift was observed. The methodologies developed in this study could provide an important contribution for the characterization of the DNA-protein interactions involved in transcriptional regulation within the context of recent developments in the molecular biology of this parasite.
Fatty acid-binding proteins (FABPs) are candidate molecules for vaccines against several parasiti... more Fatty acid-binding proteins (FABPs) are candidate molecules for vaccines against several parasitic platyhelminths. A FABP from the cestode Echinococcus granulosus (EgDf1) was expressed in Salmonella vaccine strains as a C-terminal fusion to fragment C of tetanus toxin (TetC) by using expression vector pTECH. The fusion protein was equally expressed in several attenuated vaccine strains derived from bacteria with different genetic backgrounds and different attenuating mutations. Single-dose immunization experiments with the aroA Salmonella typhimurium strain SL3261 carrying the pTECH-EgDf1 construct were conducted with mice, using both the intravenous and the oral routes. Surprisingly, the antibody response to EgDf1 and the antigen-specific cytokine production in spleen cells were stronger in mice immunized orally. Furthermore, immune mouse sera strongly reacted with fixed sections of the worm's larval stage. Analysis of the isotype distribution of the specific anti-EgDf1 antibod...
We report the isolation of a differentially expressed gene, EgTrp, which is expressed in the prot... more We report the isolation of a differentially expressed gene, EgTrp, which is expressed in the protoscoleces (PS) of Echinococcus granulosus. The experimental design was based on a differential immuno-screening of a PS kgt11 cDNA library. We used antisera raised against PS and against germinal layers, selecting those clones exclusively reactive against the former antiserum. The insert of one of the
A number of silent codon changes were made in two Escherichia coli genes. For the ompA gene, the ... more A number of silent codon changes were made in two Escherichia coli genes. For the ompA gene, the replacement of seven consecutive frequently used codons with synonymous infrequently used codons reduced the ompA mRNA level and its half-life. For the bla gene, the exchange of 24 codons for the most frequently used synonymous codons extended the bla mRNA half-life. A modification of ribosome traffic could account for these observations.
Transcription initiation from beta-lactamase, tetracycline resistance and RNA 1 promoters, presen... more Transcription initiation from beta-lactamase, tetracycline resistance and RNA 1 promoters, present in plasmid pAT153, were studied employing the abortive initiation technique. Assays appear to be promoter-specific with supercoiled and linear templates. Supercoiling enhances the isomerization rate constant of the open RNA-polymerase--promoter complex formation. Results agree with the in vivo behaviour of the corresponding promoters, and allow us to propose a hypothesis about the effect of supercoiling on transcription initiation.
The interaction between E. coli RNA polymerase and the tetR promoter from pSC101, was studied by ... more The interaction between E. coli RNA polymerase and the tetR promoter from pSC101, was studied by protection and premodification experiments, using dimethyl sulfate, methylation of single stranded cytosines, and DNAase I footprinting. Whereas qualitative and quantitative results from the chemical approach conform to patterns already displayed by other promoter systems, hypersensitive sites to DNAase I attack differ from those of other promoters. Distribution and nature of the contacts suggest that regions of the promoter sequence participates differently in complex formation. The involvement of major and minor grooves of the double helix in the complex with the enzyme, differs along the promoter. After a comparison of the results from seven different promoters, a pattern of conserved contacts seem to appear. Comparison of temperature dependence of local unwinding around the transcription start site (detected by the appearance of single stranded cytosines), and DNAase I footprinting, reveals that the process leading to stable complex formation can be achieved without disruption of base-pairing.
Two synthetic DNA sequences, carrying no other known E. coli promoter element than the consensus ... more Two synthetic DNA sequences, carrying no other known E. coli promoter element than the consensus hexamers (CH) TTGACA (CH-35) and TATAAT CH(-10), spaced by 17 bp, were inserted in pBR329, in a position enabling transcription of the complete Cmr gene. The region upstream of the Cmr transcription start was carefully cleared of w.t. promoter elements (full deletion of the wild type (w.t.) Cmr promoter upstream +2 and large portion of an upstream coding sequence). Both synthetic promoters, which differ only by the sequences of the spacers (non consensus, constrained in AT or GC) support in vivo high level Cmr gene expression. The GC rich spacer is associated with transcription start at the usual +1 position, but with the AT rich spacer, transcription starts at several places, mainly in CH(-10). Rearranged promoter sequences derived from the synthetic ones upon transformation with partly ligated plasmids, yield new insights on the role of the standard CH pair, the size of the spacer and the sequence downstream of CH(-10).
A relatively important change in UV absorption is observed upon thermal perturbation of nucleotid... more A relatively important change in UV absorption is observed upon thermal perturbation of nucleotide solutions. Comparison of these thermal perturbation spectra of nucleic acid residues with solvent perturbation spectra of the same compounds suggests that this spectral change can most probably be attributed to temperature induced hydration change of the bases. This conclusion is confirmed by the results obtained from acid-base perturbation spectra of these nucleotides as well as thermal perturbation spectra of nucleotides containing modified bases. It is shown that this temperature dependent change in UV absorption is also present in dinucleoside monophosphates. In that case, this effect is superimposed upon the well known change in absorbance due to the unstacking of the bases during heating.
The structure of the final initiation complex between E. coli RNA polymerase (RNAP) and the bla p... more The structure of the final initiation complex between E. coli RNA polymerase (RNAP) and the bla promoter from the transposon TN3 has been probed by footprinting experiments and base accessibility to dimethyl sulfate at 37 degrees C. At RNAP/promoter molar ratios "standard" for these experiments (greater than or equal to 10), the contacts on bla extend from -100 to +20, i.e. a length exceeding twice the dimension of the RNAP major axis [33]. Since footprinting at about equimolar amounts of RNAP and bla extends to the usual (-55 to +20) promoter domain, it is very likely that at least two RNAP's participate in the complex observed at tenfold higher RNAP/bla ratios. Under the latter conditions, the extended footprint (-100 to +20) is observed above 30 degrees C, whereas at 15 degrees C, only the -55 to +20 promoter area is contacted. Furthermore, gel retardation experiments show the presence of two complexes of different migration rates. We have reported earlier [21] that at the "standard" RNAP/bla ratio, transcription initiation from the bla promoter is inhibited. The correlation of this inhibition with the postulated two RNAP/bla complex suggests a regulation of bla gene expression by RNAP availability controlled for instance by growth rate. These results can be correlated with those reported in [14, 15] for the tyrT promoter. Interestingly, both promoter share significant sequence homologies.
We showed earlier that the region of the bla promoter of Tn3 protected by the RNA-polymerase (RNA... more We showed earlier that the region of the bla promoter of Tn3 protected by the RNA-polymerase (RNAP), has the normal size (about 60bp) at RNAP/promoter molar ratio r less than or equal to 2, but rises to about twice this extent as r increases. We confirm here that the species corresponding to normal and extended footprint distinguish by their electrophoretic mobilities. Furthermore, inspection of the complexes by electron microscopy confirms that at r greater than 2, the bla promoter can bind specifically a second RNAP particle, as compared to the 1:1 complex observed at r less than or equal to 2. At r greater than 2, the ability of the bla promoter to initiate transcription in vitro is repressed when compared to the complex 1:1 obtained at r less than or equal to 2. The unexpected decrease in initiation efficiency as the concentration of RNAP particles is increased, together with the striking sequence homology of the bla promoter with promoters of stable RNA, suggest that in vivo, this promoter could be regulated by growth rate.
1. Mol Biochem Parasitol. 1993 Jun;59(2):335-8. Isolation and characterization of a middle repeti... more 1. Mol Biochem Parasitol. 1993 Jun;59(2):335-8. Isolation and characterization of a middle repetitive DNA element from Echinococcus granulosus. Marín M, Garat B, Pettersson U, Ehrlich R. Departamento de Bioquímica, Facultad de Ciencias, Montevideo, Uruguay. ...
In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloni... more In order to characterize GATA transcription factors in Echinococcus granulosus, a PCR-based cloning strategy was developed. Degenerate oligonucleotides were designed for the most conserved sequence in GATA proteins that include 20 amino acids of the zinc domain. A 60 bp fragment was isolated that had high homology among this sequence and those reported in other species. An analogous sequence was obtained by performing the same procedure with DNA from the free living platyhelminth Dugesia tigrina. High stringency Southern blotting experiments confirmed the presence of this sequence in the parasite genome.
Echinococcus granulosus is the causative agent of hydatidosis, a major zoonoses that affects huma... more Echinococcus granulosus is the causative agent of hydatidosis, a major zoonoses that affects humans and herbivorous domestic animals. The disease is caused by the pressure exerted on viscera by hydatid cysts that are formed upon ingestion of E. granulosus eggs excreted by canine. Protoscoleces, larval forms infective to canine, develop asynchronously and clonally from the germinal layer (GL) of hydatid cysts. In this report, we describe the cellular organization and the appearance of differentiated structures both in nascent buds and developed protoscoleces attached to the GL. Early protoscolex morphogenesis is a highly complex and dynamic process starting from the constitution of a foramen in the early bud, around which nuclei are distributed mainly at the lateral and apical regions. Similarly, distribution of nuclei in mature protoscoleces is not homogenous but underlies three cellular territories: the suckers, the rostellar pad, and the body, that surrounds the foramen. Several nuclei are associated to calcareous corpuscles (Cc), differentiated structures that are absent in the earlier bud stages. The number of nuclei is similar from the grown, elongated bud stage to the mature protoscolex attached to the GL, strongly suggesting that there is no significant cellular proliferation during final protoscolex development. The amount of DNA per nucleus is in the same range to the one described for most other platyhelminthes. Our results point to a sequential series of events involving cell proliferation, spatial cell organization, and differentiation, starting in early buds at the GL of fertile hydatid cysts leading to mature protoscoleces infective to canine.
In this paper we examine a new distance-based method for identifying and characterizing possible ... more In this paper we examine a new distance-based method for identifying and characterizing possible interactions between biological structures and objects, with respect to the initial developmental stages of Echinococcus granulosus. By adopting the surface of the foramen as the distance reference, several interesting results have been identified, including the fact that the cell nuclei tend to be organized with respect to the foramen surface as well as the stability of the spatial distribution of these nuclei along the development stages.
Four fatty acid binding proteins (FABPs) have been described in 4 parasitic platyhelminths: Schis... more Four fatty acid binding proteins (FABPs) have been described in 4 parasitic platyhelminths: Schistosoma mansoni, Schistosoma japonicum, Fasciola hepatica and Echinococcus granulosus. FABPs form a multigenic family of cytosolic proteins widely distributed in metazoan tissues, the function of which is still poorly understood. These helminth proteins have recently received attention, since there are reports to indicate that S. mansoni and F. hepatica FABPs may be protective antigens. In addition, these proteins could play a major role in the parasites' life-cycles because platyhelminths are unable to synthesize de novo most of their lipids. We have undertaken phylogenetic and structural analyses of platyhelminth FABPs in an attempt to characterize features of biological relevance. Phylogenetically, these FABPs appear to be more closely related to those of vertebrate heart, mammary gland, muscle, retina, skin, brain and myelin, although no clear functional relationships were established between them. We describe several conserved motifs characteristic of specific groups of FABPs. Hydrophilicity, flexibility and accessibility analyses revealed several major putative epitopes for the E. granulosus FABP, EgDf1, that appear to be centred in loops of the EgDf1 3-dimensional structure modelled by molecular replacement.
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Papers by Ricardo Ehrlich