Purification and composition studies of βs-crystallin

Abstract

One of the low molecular weight proteins of bovine lens extract, designated as βs-crystallin, was purified by gel-filtration on Sephadex G-75 and chromatography on DEAE-Sephadex.

The isolated protein appeared to be homogeneous as judged by gel-electrophoresis and ultracentrifugal analyses.

The molar extinction coefficient at 278 mμ is 5·28 × 104.

The N-terminal amino acid did not react with 2,4-dinitrofluorobenzene.

There is evidence that the carboxyl-terminal group is glutamic acid.

Amino acid analysis was performed with a recovery of 100·9% of the dry weight of the protein.

The molecular weight, calculated from the amino acid composition is 28,402 and is consistent with the value determined by the approach-to-equilibrium method.

The protein contains 246 amino acid residues with the following composition: Asp22 Thr7 Ser15 Glu31 Pro9 Gly20 Ala14 Val12 Met8 Heu10 Leu14 Tyr16 Phe14 Lys12 His10 Arg16 Try5 (Cys-SH)5 (Cys-SS-Cys)2 (-CONH2)25.