Abstract
Abstract: :
Purpose: To investigate the role of the numerous aromatic amino acids in alpha–crystallin structure. Methods: Coordinate files are from the Protein Data Bank web site at http://www.rcsb.org/pdb. The Structural Classification of Proteins web site was used to retrieve representative sets of beta–sheet structures in the lens crystallins and related proteins. Our goal is to analyze the structural/functional role of aromatic amino acids to determine non–covalent interactions that participate in dimerization of similar proteins. It is generally held that these amino acids participate in side chain interactions between beta–sheets and intermolecular interactions that lead to oligermization. Therefore they are important in establishing both tertiary and quaternary protein structure. Results: The aromatic amino acids are the most conserved and have the lowest frequency of occurrence in proteins (trp, 1.32%; phe, 3.91%; tyr, 3.25%). In contrast, the beta/gamma crystallins contain ∼14–16% while the alpha–crystallins contain 19% in the first exon of each subunit and ∼10% over all. In alpha–crystallin, these amino acids are mostly found in the non–beta–sheet regions. The sequence/structural correlation with other related proteins will be presented. Conclusion: The details of the interactive properties of proteins rich in aromatic amino acids provided useful data for predicting the interactive properties in alpha–crystallin subunits. The findings support the concept that alpha–crystallin aromatic amino acids have the capacity to inhibit or participate in amyloid formation.
Keywords: crystallins • protein structure/function • chaperones