N-TERMINAL SEQUENCE OF A CORE PROTEIN FROM A BIGLYCAN ISOLATED FROM BOVINE AORTA

A biglycan was isolated from bovine aorta intima media by 4M guanidine HCl extraction of the tissue; the material was fractionated and purified by using isopycnic ultracentrifugation and DEAE Sephacel ion-exchange chromatography. Core proteins, resulting from digestion of the proteoglycan preparation with chondroitinase ABC, were resolved by SDS-polyacrylamide gel electrophoresis into three bands. The apparent molecular weight of the fast migrating major protein band was 47 kDa and the other slow-moving minor protein bands were 90 and 105 kDa. These proteins were recognized by a monoclonal anti-proteoglycan Delta Di-6S (MAb 3-B-3/Cl). The amino acid composition of 47 kDa core protein revealed a high content of aspartic acid, glutamic acid and leucine, similar to those found for biglycans isolated from bovine cartilage, rat vascular smooth muscle cell culture and human bone. The N-terminal sequence of 47 kDa core protein was determined as Asp-Glu-Glu-Ala-X-Gly-Ala-Glu-Thr-Thr-X-Gly-Ile-Pro-Asp which is identical to the sequence of bovine articular cartilage biglycan. The proteoglycan had two glycosaminoglycan chains.