Alkylation of rat lens crystallins with iodoacetamide

Alkylation of lens proteins with iodoacetamide during homogenization of tissue (50 millimolar excess) immediately followed by gel-permeation chromatography yielded a crystallin population devoid of βH-crystallin. This result occurred in lens homogenates from both young (100 g) and older (400 g) male rats. BetaH-crystallin was not converted to insoluble protein with alkylation. Each crystallin fraction reacted with radioactive iodoacetamide in proportion to sulfhydryl content; at a ratio of 1 mg iodoacetamide/mg protein total free-sulfhydryl of the crystallins had reacted after 1 hr at pH 8, 25°C. Alkylated α-, βL-' and y-crystallin fractions demonstrated no altered chromatographic behavior on Sephacryl S-200; only alkylated βH-crystallin was altered so that it co-chromatographed with control or alkylated βL-crystallin.