Protein-Lipid Interactions IV 3604-Pos Board B332 To be or not to be in Membrane Domains: Transbilayer Asymmetry and Sphingomyelin-Dependent Preferential Partitioning of the Acetylcholine Receptor Vanesa L. Perillo 1,2 , D. Alejandro Pen˜alva 1,2 , Marta I. Aveldan˜o 1,2 , Francisco J. Barrantes 3 , Silvia S. Antollini 1,2 . 1 Instituto de Investigaciones Bioquimicas de Bahia Blanca, Bahia Blanca, Argentina, 2 Universidad Nacional del Sur, Bahia Blanca, Argentina, 3 Biomedical Research Institute, UCA-CONICET, Buenos Aires, Argentina. The preferential partitioning of the nicotinic acetylcholine receptor (AChR) in liquid-ordered (Lo) domains, heterogeneous membrane domains commonly known as rafts, is thought to be a part of its clustering mechanism. Previous studies from our group have shown that AChR lacks preference for Lo domains when reconstituted in sphingomyelin (SM), cholesterol (Chol) and POPC (1:1:1) model systems (Bermu´dez et al., 2010). Here we study the effect on the possible Lo-preferential partitioning of purified AChR reconstituted in two different model systems (POPC:Chol, 1:1 and POPC:Chol:SM, 1:1:1) under: a) induced transbilayer asymmetry, resulting from addition of brain sphingomyelin (bSM) to the external hemilayer; and b) the presence of different pure SM species in the model membrane (bSM, 16:0-SM, 18:0-SM or 24:1- SM). AChR distribution was evaluated by fluorescence resonance energy transfer efficiency between the AChR intrinsic fluorescence and Laurdan or de- hydroergosterol fluorescence, and also by determining the presence of AChR in detergent-resistant and detergent-soluble domains (1% Triton X-100, 4 C). Both studies show that the induction of transbilayer asymmetry or the presence of 16:0-SM or 18:0-SM, as opposed to bSM or 24:1-SM, leads to a preferential partitioning of AChR in Lo domains. Thus, the localization of AChR in Lo do- mains strongly depends on the characteristics of the host lipid membrane. 3605-Pos Board B333 Formation of Giant Unilamellar Vesicles Containing Active Proteins Isabelle Motta, Vladimir Adrien, Andrea Gohlke, Pincet Frederic. Ecole Normale Superieure, Paris, France. Giant unilamellar vesicles (GUVs), composed of a phospholipid bilayer, are often used as a model for cell membranes. However the study of proteo- membrane interactions in this system is limited because the incorporation of in- tegral and lipid-anchored proteins into the GUVs remains challenging. All pre- existing protocols either produce membranes with a very low protein density or are tailored to specifically support the inclusion of a particular protein. We recently developed a simple generic method to incorporate protein in GUVs. It does not require specific lipids or reagents, works in physiological conditions with high concentrations of protein, and the resulting proteo-GUVs can be micromanipulated. Moreover, our protocol is not limited to a narrow range of protein substrates; indeed we have already successfully incorporated two trans-membrane proteins and one lipid-anchored peripheral protein. These first proof-of-principle proteins present different types of challenges and thus demonstrate the broad utility of our method. TolC is an integral membrane protein and part of a heterotrimer, that together comprise a major multidrug efflux pump in E coli. The neuronal t-SNARE is a protein complex with a single transmembrane domain that mediates membrane fusion. Because of its propen- sity to aggregate t-SNARE is usually not functional after insertion in GUVs. To study lipidated proteins, we incorporated a modified form of the autophagy protein GABARAP L1, which we anchored it to the membrane via a cysteine-maleimide covalent bond. In each case, we verified that the proteins remain active after incorporation. We also verified their mobility by performing diffusion measurements via fluorescence recovery after photo bleaching (FRAP) experiments on micromanipulated GUVs. The diffusion coefficients are in agreement with previous data. 3606-Pos Board B334 Influence of a Central Tryptophan and of Cholesterol on the Properties of Defined Transmembrane Helical Peptides Vasupradha Suresh Kumar, Bethany P. Doss, Denise V. Greathouse, Roger E. Koeppe II. University of Arkansas, Fayetteville, AR, USA. GWALP23 (acetyl-GGALW 5 LALALALALALALW 19 LAGA-amide) pro- vides a favorable host framework for investigations of the influence of guest amino acids, for example a third, centrally located, Trp residue, within the hydrophobic core of a well characterized transmembrane helix. It is crucial to note that the orientation and rotation of GWALP23 are sensitive to single- residue replacements, in part because the membrane-spanning helix exhibits only limited dynamic averaging of solid-state NMR observables such as the 2 H quadrupolar splitting (Biophys. J. 101, 2939). We introduced a Trp res- idue into position 12 or 13 of GWALP23 (replacing either L12 or A13) and incorporated specific 2 H-Ala labels within the helical core sequence. Solid- state 2 H NMR spectra of GWALP23-W12 reveal that the peptide remains helical and retains a dominant preferred tilted transmembrane orientation with only a low extent of dynamic averaging, comparable to GWALP23 itself. Indeed, the tilt and dynamics of GWALP23-W12 are quite similar to the values observed for GWALP23 in DMPC bilayer membranes. We have analyzed the dynamics of the peptide helices using a modified Gaussian treatment as well as a semi-static treatment. The results indicate that a central Trp residue at posi- tion 12 does not appreciably perturb the properties of bilayer-spanning GWALP23. (By contrast, Arg-12 or Lys-12, when charged, induces multi- state behavior for GWALP23 in bilayer membranes [PNAS 110, 1692].) Addi- tionally, we are investigating the influence of cholesterol upon the properties of membrane-spanning GWALP23, GWALP23-W12 and GWALP23-K12. 3607-Pos Board B335 Regulation of K-RAS Membrane Association: Calmodulin Versus PDEd Katrin Weise 1 , Benjamin Sperlich 1 , Shobhna Kapoor 1 , Gemma Triola 1,2 , Herbert Waldmann 1,2 , Roland Winter 1 . 1 TU Dortmund University, Dortmund, Germany, 2 Max Planck Institute of Molecular Physiology, Dortmund, Germany. K-Ras is a small GTPase that plays a critical role in human cancer cell biology. Selective membrane localization and clustering of K-Ras4B into microdomains are mediated by its polybasic farnesylated C-terminus. The importance of the subcellular distribution for the signaling activity of K-Ras4B became apparent from recent in vivo studies [1]. PDEd and the Ca 2þ -binding protein calmodulin (CaM) are known to function as potential binding partners for farnesylated Ras proteins, leading to a modulation of the spatiotemporal organization of K-Ras4B. The latest study of our group showed that PDEd is not able to extract K-Ras4B from model raft membranes; instead, an effective delivery of PDEd- solubilized K-Ras4B to the plasma membrane was proposed [2]. Compared to PDEd, CaM exhibits additional interaction sites to the G-domain of K-Ras4B and was shown not to be required for the transport of K-Ras4B to the plasma membrane. Thus, it was suggested that calmodulin dissociates K-Ras4B from membranes [3]. However, the exact role of CaM in the intracellular localization and dynamics of K-Ras4B still remains elusive. In the present approach, the influence of CaM on the interaction of GDP- and GTP-loaded K-Ras4B with anionic model raft membranes has been investi- gated by a combination of different spectroscopic and imaging techniques. The results suggest that binding of the acidic CaM to the polybasic stretch of K-Ras4B reverses its charge, leading to repulsion of the complex from anionic membranes. Since one farnesyl anchor alone is not sufficient to stably anchor Ras proteins to membranes, CaM would be able to dissociate K-Ras4B from plasma membranes, contrary to PDEd. References: [1] Ismail SA et al. (2011) Nat. Chem. Biol. 7: 942-949. [2] Weise K et al. (2012) J. Am. Chem. Soc. 134: 11503-11510. [3] Bhagatji P et al. (2010) Biophys. J. 99: 3327-3335. 3608-Pos Board B336 Influence of Glutamic Acid Residues on the Properties of Model Membrane-Spanning Helices Venkatesan Rajagopalan, Denise V. Greathouse, Roger E. Koeppe II. University of Arkansas, Fayetteville, AR, USA. GWALP23 (acetyl-GGALW 5 LALALALALALALW 19 LAGA- amide) is a constructive model peptide for investigations of single-residue effects on protein-lipid interactions and the properties of membrane-spanning helices (J.Biol. Chem. 285, 31723). GWALP23 has favorable properties in bilayer membranes because the peptide exhibits only limited dynamic averaging of NMR observables such as the 2 H quadrupolar splitting or the 15 N- 1 H dipolar coupling (Biophys. J. 101, 2939). To investigate the potential influence of negatively charged glutamic acid side chains upon system properties, we have substituted a single Leu residue with Glu at different positions and incorporated specific 2 H-Ala labels in the core of the single-Trp peptide Y 5 GWALP23 (see Biochemistry 51, 2044). Solid state 2 H NMR experiments showed well defined 2 H quadrupolar splittings for Y 5 GWALP23-E16 in the pH range from 4.0 to 9.0, suggesting that the peptide helix is well oriented in DOPC lipid bilayers. The E16-containing peptide seems to exhibit multi-state behavior at pH 10.9, in bilayers formed by ether-linked lipids, suggesting a pKa that is above pH 9 for the E16 side chain. The rather modest shift in the 2 H quadrupolar splittings suggests that the orientation of the transmembrane peptide helix changes rather little at high pH. It is conceivable that the close proximity of E16 to W19 could provide stability to the neutral peptide helix and perhaps influence the pKa of E16. The molecular cousin having E14 instead of E16 shows multi-state behavior from pH 4.0 to pH 10.9 rendering pKa Wednesday, February 19, 2014 711a
Wednesday, February 19, 2014
Protein-Lipid Interactions IV
3604-Pos Board B332
To be or not to be in Membrane Domains: Transbilayer Asymmetry and
Sphingomyelin-Dependent Preferential Partitioning of the Acetylcholine
Receptor
Vanesa L. Perillo1,2, D. Alejandro Peñalva1,2, Marta I. Aveldaño1,2,
Francisco J. Barrantes3, Silvia S. Antollini1,2.
1
Instituto de Investigaciones Bioquimicas de Bahia Blanca, Bahia Blanca,
Argentina, 2Universidad Nacional del Sur, Bahia Blanca, Argentina,
3
Biomedical Research Institute, UCA-CONICET, Buenos Aires, Argentina.
The preferential partitioning of the nicotinic acetylcholine receptor (AChR) in
liquid-ordered (Lo) domains, heterogeneous membrane domains commonly
known as rafts, is thought to be a part of its clustering mechanism. Previous
studies from our group have shown that AChR lacks preference for Lo domains
when reconstituted in sphingomyelin (SM), cholesterol (Chol) and POPC
(1:1:1) model systems (Bermúdez et al., 2010). Here we study the effect on
the possible Lo-preferential partitioning of purified AChR reconstituted in
two different model systems (POPC:Chol, 1:1 and POPC:Chol:SM, 1:1:1)
under: a) induced transbilayer asymmetry, resulting from addition of brain
sphingomyelin (bSM) to the external hemilayer; and b) the presence of different
pure SM species in the model membrane (bSM, 16:0-SM, 18:0-SM or 24:1SM). AChR distribution was evaluated by fluorescence resonance energy
transfer efficiency between the AChR intrinsic fluorescence and Laurdan or dehydroergosterol fluorescence, and also by determining the presence of AChR
in detergent-resistant and detergent-soluble domains (1% Triton X-100, 4 C).
Both studies show that the induction of transbilayer asymmetry or the presence
of 16:0-SM or 18:0-SM, as opposed to bSM or 24:1-SM, leads to a preferential
partitioning of AChR in Lo domains. Thus, the localization of AChR in Lo domains strongly depends on the characteristics of the host lipid membrane.
3605-Pos Board B333
Formation of Giant Unilamellar Vesicles Containing Active Proteins
Isabelle Motta, Vladimir Adrien, Andrea Gohlke, Pincet Frederic.
Ecole Normale Superieure, Paris, France.
Giant unilamellar vesicles (GUVs), composed of a phospholipid bilayer, are
often used as a model for cell membranes. However the study of proteomembrane interactions in this system is limited because the incorporation of integral and lipid-anchored proteins into the GUVs remains challenging. All preexisting protocols either produce membranes with a very low protein density or
are tailored to specifically support the inclusion of a particular protein. We
recently developed a simple generic method to incorporate protein in GUVs.
It does not require specific lipids or reagents, works in physiological conditions
with high concentrations of protein, and the resulting proteo-GUVs can be
micromanipulated. Moreover, our protocol is not limited to a narrow range
of protein substrates; indeed we have already successfully incorporated two
trans-membrane proteins and one lipid-anchored peripheral protein.
These first proof-of-principle proteins present different types of challenges and
thus demonstrate the broad utility of our method. TolC is an integral membrane
protein and part of a heterotrimer, that together comprise a major multidrug
efflux pump in E coli. The neuronal t-SNARE is a protein complex with a single
transmembrane domain that mediates membrane fusion. Because of its propensity to aggregate t-SNARE is usually not functional after insertion in GUVs. To
study lipidated proteins, we incorporated a modified form of the autophagy
protein GABARAP L1, which we anchored it to the membrane via a
cysteine-maleimide covalent bond. In each case, we verified that the proteins
remain active after incorporation. We also verified their mobility by performing
diffusion measurements via fluorescence recovery after photo bleaching
(FRAP) experiments on micromanipulated GUVs. The diffusion coefficients
are in agreement with previous data.
3606-Pos Board B334
Influence of a Central Tryptophan and of Cholesterol on the Properties
of Defined Transmembrane Helical Peptides
Vasupradha Suresh Kumar, Bethany P. Doss, Denise V. Greathouse,
Roger E. Koeppe II.
University of Arkansas, Fayetteville, AR, USA.
GWALP23 (acetyl-GGALW5LALALALALALALW19LAGA-amide) provides a favorable host framework for investigations of the influence of guest
amino acids, for example a third, centrally located, Trp residue, within the
hydrophobic core of a well characterized transmembrane helix. It is crucial
to note that the orientation and rotation of GWALP23 are sensitive to singleresidue replacements, in part because the membrane-spanning helix exhibits
only limited dynamic averaging of solid-state NMR observables such as
the 2H quadrupolar splitting (Biophys. J. 101, 2939). We introduced a Trp res-
711a
idue into position 12 or 13 of GWALP23 (replacing either L12 or A13) and
incorporated specific 2H-Ala labels within the helical core sequence. Solidstate 2H NMR spectra of GWALP23-W12 reveal that the peptide remains
helical and retains a dominant preferred tilted transmembrane orientation
with only a low extent of dynamic averaging, comparable to GWALP23 itself.
Indeed, the tilt and dynamics of GWALP23-W12 are quite similar to the values
observed for GWALP23 in DMPC bilayer membranes. We have analyzed the
dynamics of the peptide helices using a modified Gaussian treatment as well as
a semi-static treatment. The results indicate that a central Trp residue at position 12 does not appreciably perturb the properties of bilayer-spanning
GWALP23. (By contrast, Arg-12 or Lys-12, when charged, induces multistate behavior for GWALP23 in bilayer membranes [PNAS 110, 1692].) Additionally, we are investigating the influence of cholesterol upon the properties
of membrane-spanning GWALP23, GWALP23-W12 and GWALP23-K12.
3607-Pos Board B335
Regulation of K-RAS Membrane Association: Calmodulin Versus PDEd
Katrin Weise1, Benjamin Sperlich1, Shobhna Kapoor1, Gemma Triola1,2,
Herbert Waldmann1,2, Roland Winter1.
1
TU Dortmund University, Dortmund, Germany, 2Max Planck Institute of
Molecular Physiology, Dortmund, Germany.
K-Ras is a small GTPase that plays a critical role in human cancer cell biology.
Selective membrane localization and clustering of K-Ras4B into microdomains
are mediated by its polybasic farnesylated C-terminus. The importance of the
subcellular distribution for the signaling activity of K-Ras4B became apparent
from recent in vivo studies [1]. PDEd and the Ca2þ-binding protein calmodulin
(CaM) are known to function as potential binding partners for farnesylated
Ras proteins, leading to a modulation of the spatiotemporal organization of
K-Ras4B. The latest study of our group showed that PDEd is not able to extract
K-Ras4B from model raft membranes; instead, an effective delivery of PDEdsolubilized K-Ras4B to the plasma membrane was proposed [2]. Compared to
PDEd, CaM exhibits additional interaction sites to the G-domain of K-Ras4B
and was shown not to be required for the transport of K-Ras4B to the plasma
membrane. Thus, it was suggested that calmodulin dissociates K-Ras4B from
membranes [3]. However, the exact role of CaM in the intracellular localization
and dynamics of K-Ras4B still remains elusive.
In the present approach, the influence of CaM on the interaction of GDP- and
GTP-loaded K-Ras4B with anionic model raft membranes has been investigated by a combination of different spectroscopic and imaging techniques.
The results suggest that binding of the acidic CaM to the polybasic stretch of
K-Ras4B reverses its charge, leading to repulsion of the complex from anionic
membranes. Since one farnesyl anchor alone is not sufficient to stably anchor
Ras proteins to membranes, CaM would be able to dissociate K-Ras4B from
plasma membranes, contrary to PDEd.
References:
[1] Ismail SA et al. (2011) Nat. Chem. Biol. 7: 942-949.
[2] Weise K et al. (2012) J. Am. Chem. Soc. 134: 11503-11510.
[3] Bhagatji P et al. (2010) Biophys. J. 99: 3327-3335.
3608-Pos Board B336
Influence of Glutamic Acid Residues on the Properties of Model
Membrane-Spanning Helices
Venkatesan Rajagopalan, Denise V. Greathouse, Roger E. Koeppe II.
University of Arkansas, Fayetteville, AR, USA.
GWALP23 (acetyl-GGALW5LALALALALALALW19LAGA- amide) is a
constructive model peptide for investigations of single-residue effects on
protein-lipid interactions and the properties of membrane-spanning helices
(J.Biol. Chem. 285, 31723). GWALP23 has favorable properties in bilayer
membranes because the peptide exhibits only limited dynamic averaging of
NMR observables such as the 2H quadrupolar splitting or the 15N-1H dipolar
coupling (Biophys. J. 101, 2939). To investigate the potential influence of
negatively charged glutamic acid side chains upon system properties, we
have substituted a single Leu residue with Glu at different positions and
incorporated specific 2H-Ala labels in the core of the single-Trp peptide
Y5GWALP23 (see Biochemistry 51, 2044). Solid state 2H NMR experiments
showed well defined 2H quadrupolar splittings for Y5GWALP23-E16 in the
pH range from 4.0 to 9.0, suggesting that the peptide helix is well oriented in
DOPC lipid bilayers. The E16-containing peptide seems to exhibit multi-state
behavior at pH 10.9, in bilayers formed by ether-linked lipids, suggesting a
pKa that is above pH 9 for the E16 side chain. The rather modest shift in the
2
H quadrupolar splittings suggests that the orientation of the transmembrane
peptide helix changes rather little at high pH. It is conceivable that the close
proximity of E16 to W19 could provide stability to the neutral peptide helix
and perhaps influence the pKa of E16. The molecular cousin having E14 instead
of E16 shows multi-state behavior from pH 4.0 to pH 10.9 rendering pKa
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Throughout the last two centuries, natural resources have influenced the development of sovereignty, law, and trade around the globe. Protecting, owning, and extracting natural resources have emerged as critical issues, resulting in disputes over social and economic rights and competing religious and economic views of resources. These matters have mobilized indigenous actors, local authorities, national agencies, and international bodies, thus interconnecting various communities on multiple scales of power and historical analysis. Resource extraction and trade profoundly altered local and regional social, political and economic structures, often provoking resistance and pushback against marginalization and dispossession. They also shaped regional environments through material transformations including the expansion of extractive infrastructures and the (toxic) legacies left behind by resource production. Since extraction frequently took place far away from the sites of consumption, it suggests an externalization and racialization of risk.
The various modes of exploitation, negligence and abandonment of commodity frontiers require an approach that is locally grounded without losing sight of the patterns and systemic nature of resource development.
This international conference invites scholars to examine the history and political ecology of various resources—biotic, animal, or mineral—in the modern era. It calls on scholars to analyze these resources, their trade and regulation, and their impact on national and world trade in the nineteenth and twentieth century. What roles did natural resources such as petroleum, copper, palm oil or water play in the field of law, the environment, and the economy? In what ways did these resources influence and transform national and international histories? What is the relationship between the past and our contemporary concerns with global supply structures and the volatility of markets. We particularly welcome papers that highlight the role of local actors; consider multinational firms operating during critical junctures such as military conflicts and across the era of decolonization; explore case studies within and beyond the Western hemisphere; and adopt an interdisciplinary approach to studying the global history of natural resources and their links to the worlds of politics, strategy, law, and the economy.
Potential papers can address (though are not limited to) the following:
- The social and ecological costs of extraction in local and global contexts
- International commodity schemes and control acts / monopolies and the manipulation of markets / systems of “imperial preference”
- The role of smallholders and non-western actors at commodity frontiers, as intermediaries, smugglers, consumers and producers
- Ruptures and continuity of resource production and trade across political junctures, including military conflicts and decolonization
- National sovereignty and “layered sovereignty” at resource frontiers, including the power and political leverages of firms
- Scientific-technical expertise and the role of knowledges
- Resources, land rights and nationalism
- The role of national and international institutions – from botanic gardens to the ILO
- The history of labour and work migration, forms of indentured and unfree labour
- Gender dimensions of land ownership, resource extraction, processing, and consumption
- Discourses of scarcity and their reception
- The Cooperative Movement and alternatives modes of commodity production and social organization
- Postcolonial/National Development Programs, Five-Year Plans in the Communist countries and the Global South
Introduction Hydrogen has been regarded as an ideal energy carrier for the future. One of the most promising renewable approaches for the production of hydrogen is photocatalytic water splitting over Titanium dioxide [1, 2]. However, the limited efficiency of TiO2 for hydrogen production via water splitting restricts the practical application of tiania. One of the efficient approaches applied to overcome shortcomings is immobilization of TiO2 particles on a highly porous zeolite. The abundance, high chemical stability, excellent absorption capacity, special ion-exchange ability and low extraction cost of clinoptilolite make this kind of zeolite a very attractive support [3]. The reproducibility of extracted samples and the difficulty in obtaining homogeneous material are the main drawbacks in the application of natural zeolites. To overcome these problems, chemical treatments such as ion exchange have been applied. The ion exchange treatment can affect the chemical and sorption char...
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Uganda, an enclave in the Great Lakes region, has prioritized animal production in the Programme for Modernization of Agriculture (PMA) put in place in 2000 to alleviate poverty. The French cooperation participates in the PMA implementation by developing activities in the dairy sector in the southwestern Mbarara region, where close to one million cattle contribute to the greatest amount of milk to Kampala, the capital city. The high prevalence of tuberculosis and brucellosis registered in cattle farming has raised public concern on the zoonotic risk of these diseases. Results presented in this study confirm high animal prevalence of both tuberculosis and brucellosis, and surveys carried out in the human population concluded that the crucial public health problem of these diseases is more pronounced in Mbarara than in Kampala, due to a lower consumption of raw milk in the capital city. Recommendations highlight on a better sensitization on the risks associated with raw milk consumpti...
Міністерство Освіти та Науки України Український державний університет імені М. Драгоманова «Коли Захід зустрів Схід: наукова конференція присвячена пам'яті Андрія Ковалівського», 2024