Structural similarity of hyaluronate binding proteins in brain and cartilage

A glial hyaluronate-binding protein (GHAP) was isolated from human brain white matter by affinity chromatography on immobilized hyaluronate. The 60 kDa protein appeared remarkably homogeneous by reversed-phase high pressure liquid chromatography analysis. Four cyanogen bromide peptides and 10 tryptic peptides were characterized by amino acid sequence, a total of 12 sequences since overlaps were found between 2 cyanogen bromide and 2 tryptic peptide sequences. Two sequences of brain GHAP had similarity with rat link protein, a hyaluronate binding protein in cartilage. The region of similarity was contained in the evolutionary conserved COOH-terminal half of link protein which is involved in the binding of hyaluronate. The remaining 10 amino acid sequences of brain GHAP had no similarity with link protein, nor with previously reported protein sequences. The findings suggest that the hyaluronate binding domains of such diverse proteins as brain GHAP and cartilage link protein are similar, probably due to the fact that hyaluronic acid is highly conserved in evolution.