SOME PROPERTIES OF LOW-MOLECULAR WEIGHT ALPHA-CRYSTALLIN FROM NORMAL HUMAN LENS - COMPARISON WITH BOVINE LENS

Low molecular weight .alpha.-crystallin (6 .times. 105-9 .times. 105 daltons) was isolated from normal human lenses of various ages and from bovine lenses by gel filtration on Sephadex G-100 followed by chromatography on an Agarose A-15 m-column. The elution pattern obtained from the Agarose column for the human and bovine lenses was identical. A value of 2.5 .times. 10-7 cm2/s at 22.degree. C for the translational diffusion coefficient was observed for both the human and the bovine fractions using laser light scattering experiments. Similar far UV circular dichroism (CD) spectra were obtained from human and bovine lenses. The near UV spectrum of .alpha.-crystallin showed a complex wavelength profile (vibronic structure) between 240-300 nm. These vibronic transitions arose from tryptophan, tyrosine and phenylalanine residues. The .alpha.-crystallin wavelength profiles from bovine and normal human lenses of various ages were the same. Dissociating the low molecular weight .alpha.-crystallin subunits with guanidine-HCl greatly altered the near ultraviolet spectrum, indicating conformational changes. Removal of the guanidine-HCl yielded a far UV spectrum indistinguishable from that of native .alpha.-crystallin. The native near UV spectrum could not be regenerated upon removal of the guanidine-HCl. No conformational changes were observed upon addition or removal of Ca2+. From the similarity in the elution patterns, translational diffusion coefficient and near ultraviolet CD wavelength profiles of bovine and human low molecular weight .alpha.-crystallin, it seems that, in spite of some differences in amino acid composition, both fractions possess similar secondary and tertiary structures.