Isolation of glycoproteins from bovine nuchal ligament

Soluble substances in the bovine nuchal ligament were removed by preliminary extractions with a buffer and dilute alkali solution. The insoluble residue was then extracted with 6 M guanidine HCl and with 6 M guanidine HCl containing a reducing agent (20 mM dithiothreitol) successively. Each of the two extracts contained a glycoprotein; that in the first extract was designated Glycoprotein A and that in the second Glycoprotein B. They were purified by ion-exchange chromatography and gel filtration till essentially homogeneous. Both proteins had similar molecular weights of 35,000 in SDS-polyacrylamide gel electrophoresis and by gel filtration, and their chemical compositions resembled each other closely. It is suggested that Glycoprotein B was present in the native state as a disulfide-bonded, aggregated form of Glycoprotein A. The compounds also showed similarity with the microfibrillar glycoprotein(s) previously reported in bovine nuchal ligament extracts.