Invited: Prediction of protein function

A genome sequence embodies the potential life of an organism, but implementation of genetic information depends on the functions of the proteins that it encodes. Many proteins of known sequence and even of known structure present challenges to understanding their function. In some cases genes responsible for diseases have been identified but their specific functions are unknown. Annotation of a genome involves assignment of functions to gene products, in most cases on the basis of amino acid sequence alone, in the absence of experimental information. Protein structures from structural genomics projects are invaluable for function assignment. Nevertheless, prediction of protein function remains a difficult problem. Some methods provide reasonable guesses, but no method is foolproof. Moreover, even when it is possible to ascribe a particular function to a gene product, the protein may have multiple functions. An underlying problem has been that function is in many cases an ill-defined concept.