Subunit composition of delta-crystallin from embryonic chick lens. Analysis of methionine-containing tryptic peptides and cyanogen bromide peptides.
The predominant protein in the embryonic chick lens, delta-crystallin, is composed of four subunits with molecular weights near 50,000. The degree to which these 4 polypeptides are the same or dissimilar was explored in delta crystallin purified from 15-day-old embryonic chick lenses by relating the numbers of methionine-containing tryptic peptides and cyanogen bromide (CNBr) peptides derived from the native protein to the average number of methionine residues per subunit. Amino acid analyses indicated that 1 mol of native delta-crystallin contains approximately 32 methionine residues, leading to an average of 8 methionine residues per subunit. Approximately equal amounts of 8 methionine-containing tryptic peptides were resolved by two-dimensional thin layer separation on cellulose sheets and by isoelectric focusing in polyacrylamide gels. Nine CNBr peptides were resolved by a combination of electrophoresis in sodium dodecyl sulfate (SDS)-polyacrylamide gels and chromatography on SDS-hydroxylapatite columns. The additive molecular weight of the 9 CNBr peptides was very close to the delta-crystallin subunit molecular weight of 50,000. Thus, the subunits of 15-day-old embryonic chick delta-crystallin have similar sequence of encoded amino acids.
D000818:Animals; D002642:Chick Embryo; D002855:Chromatography, Thin Layer; D003459:Crystallins; D003488:Cyanogen Bromide; D006714:Homoserine / Q000032:analysis; D008715:Methionine / Q000032:analysis; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D014357:Trypsin
D003459:Crystallins; D010446:Peptide Fragments; D006714:Homoserine; D008715:Methionine; D014357:Trypsin; D003488:Cyanogen Bromide