Isolation and partial characterization of a glial hyaluronate-binding protein.

A glial hyaluronate-binding protein (GHAP) with an isoelectric point of 4.3-4.4 was isolated from human brain white matter. The 60-kDa glycoprotein appeared to be quite resistant to proteolysis, and comparison with GHAP from a viable glioma removed at surgery showed that the protein isolated from autopsy material was not a degradation product resulting from postmortem autolysis. The protein was localized immunohistochemically with mouse monoclonal and rabbit polyclonal antibodies in cerebral white matter. Only small amounts could be found in the gray matter. After enzymatic deglycosylation, an immunoreactive 47-kDa polypeptide was obtained. Two amino acid sequences of GHAP showed a striking similarity (up to 89%) with a highly conserved region of cartilage proteins (bovine nasal cartilage proteoglycan and rat and chicken link protein). However, the amino acid composition and other amino acid sequences suggested that there are also differences between brain-specific GHAP and cartilage proteins.