On the structure of proteoglycan core

Core protein from bovine nasal proteoglycan has been obtained by cyanogen bromide cleavage and by removal of most of the glycosaminoglycan side chains by hydrogen fluoride treatment. Amino acid analysis of the cyanogen bromide fragment shows it to consist mainly of proline, serine, glycine and glutamic acid (glutamine). End-group analyses of the fragment and HF stripped core reveal and N-terminal residue to be valine in each case. The stripped core has been subjected to sequencing and some sequential information is presented. Based upon the amino acid analysis, sequence information and other properties, conformation analysis indicates that the most likely conformation is that of a flexible extended chain containing β-turns. The existence of a common N-terminal residue indicates that it is the C-terminal region which lies in the region of the hyaluronic acid backbone in intact proteoglycan. Furthermore, enzymatic cleavage of core protein which occurs in proteoglycan turnover, aging and degenerative diseases, probably does not occur by a stepwise cleavage from the N terminus of proteoglycan but by a more drastic degradation process.