Three‐dimensional model and quaternary structure of the human eye lens protein γS‐crystallin based on β‐ and γ‐crystallin X‐ray coordinates and ultracentrifugation

Open Access
Publisher Website
Google Scholar
Abstract
A 3‐dimensional model of the human eye lens protein γS‐crystallin has been constructed using comparative modeling approaches encoded in the program COMPOSER on the basis of the 3‐dimensional structure of γ‐crystallin and β‐crystallin. The model is biased toward the monomeric γB‐crystallin, which is more similar in sequence. Bovine γS‐crystallin was shown to be monomeric by analytical ultracentrifugation without any tendency to form assemblies up to concentrations in the millimolar range. The connecting peptide between domains was therefore built assuming an intramolecular association as in the monomeric γ‐crystallins. Because the linker has 1 extra residue compared with γB and βB2, the conformation of the connecting peptide was constructed by using a fragment from a protein database. γS‐crystallin differs from γB‐crystallin mainly in the interface region between domains. The charged residues are generally paired, although in a different way from both β‐ and γ‐crystallins, and may contribute to the different roles of these proteins in the lens.