Bovine lens crystallins do contain helical structure: a circular dichroismstudy

In order to settle a recent discussion on the secondary structure of lens c rystallins, we have measured the circular dichroism (CD) spectra of alpha-, beta(H)-, and beta(L)-crystallin from 178 to 250 nm and of gamma-crystalli n from 168 to 250 nm. The results were analysed by means of a newly develop ed algorithm that almost doubles the reliability of secondary structure pre diction and that allows discrimination between alpha- and 3(10)-helical, an d between extended and polyproline beta-type structure. The results indicat e that the crystallins studied contain a non-negligible amount of alpha-hel ical 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 ca ses, the helices may play a role in DNA binding by the crystallins. (C) 199 9 Elsevier Science B.V. All rights reserved.