Bovine lens crystallins do contain helical structure: a circular dichroism study.
In order to settle a recent discussion on the secondary structure of lens crystallins, we have measured the circular dichroism (CD) spectra of alpha-, beta(H)-, and beta(L)-crystallin from 178 to 250 nm and of gamma-crystallin from 168 to 250 nm. The results were analysed by means of a newly developed algorithm that almost doubles the reliability of secondary structure prediction and that allows discrimination between alpha- and 3(10)-helical, and between extended and polyproline beta-type structure. The results indicate that the crystallins studied contain a non-negligible amount of alpha-helical structure, although at least 50% of it is in the form of single and/or distorted loops. In alpha-crystallin, which is related to the chaperones, the helical content is lower than in beta- and gamma-crystallin. In some cases, the helices may play a role in DNA binding by the crystallins.
Department of Biophysics, Free University, De Boelelaan 1081, 1081 HV, Amsterdam, Netherlands. michael@nat.vu.nl
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D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D012984:Software
D003459:Crystallins