Identification of cyanogen bromide-fragments of the protein core of bovine nasal cartilage proteoglycan monomer

Abstract

Cyanogen bromide treatment of bovine nasal cartilage proteoglycan monomer gave rise to three major fractions (CN-1 to CN-3), isolated by Sepharose CL-6B chromatography. The uronate-rich fraction in the void volume (CN-1) digested with chondroitinase ABC (C treatment) yielded a fragment (CN-1 C/6B) with a unique N-terminal sequence. The same fraction, when digested sequentially by chondroitinase ABC and trypsin (CT treatment), was resolved into two distinct fractions, CN-1 CT/6B-1 and CN-1 CT/6B-2. CN-1 CT/6B-1 consisted in a keratan sulfate-rich region, representing the N-terminal moiety of the CN-1 fraction; these data suggested, according to the model of the proteoglycan monomer structure described by Heinegard, D. and Axelsson, I. (1977) J. Biol. Chem. 252, 1971–1979, that its C-terminal moiety is localized at the end of the core bearing the chondroitin sulfate chains. CN-1 CT/6B-2 contained two fragments from the chondroitin sulfate-bearing region: one of them has been submitted to Edman degradation. The CN-2 fraction upon cbondroitinase and trypsin treatments gave rise to a keratan-bearing region (CN-2 CT/6B-1) and a mannose-rich region (CN-2 CT/6B-2). After reduction and alkylation of CN-2, the N-terminal sequence of the isolated major fragment (CN-2 RA/6B-1) was determined. The CN-3 fraction revealed a pattern upon electrophoresis similar to that of the cyanogen bromide-treated hyalurouic acid-binding region.