Classification and Function Prediction of Proteins Using Diagnostic Amino Acid Patterns

Protein sequence similarities offer a convenient means for the classification and identification of protein families and superfamilies. Frequently, proteins descended from a common ancestor preserve their basic three-dimensional conformations even when they have accumulated large numbers of amino acid substitutions and short insertions or deletions. These may prohibit establishment of homology or evolutionary relationships by traditional global sequence alignment means. Limited regions of sequence similarity can also be the result of evolutionary convergence driven by a need for a common function. Regardless of whether divergent or convergent evolution played a role in the appearance of local sequence similarities, these confined regions of similarity can provide insight into structural and functional relationships of proteins that otherwise fail to show significant similarity by global alignment methods.