The Distribution of Carbohydrate Groups in Rat Skin Collagen
J. Hector Aguilar 1, H. Gayle Jacobs 1, William T. Butler 1, and Leon W. Cunningham 1
From the
1 From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, and The Institute of Dental Research, The University of Alabama in Birmingham, Birmingham, Alabama 35233
Glycopeptides from soluble rat skin collagen were prepared by sequential digestion with collagenase and trypsin. The isolation of the major glycopeptides was accomplished with gel filtration and ion exchange chromatography.
The glycohexapeptide, Gly-Met-Hyl (Gal-Glc)-Gly-His-Arg, has previously been characterized in digests of various vertebrate collagens studied in this and other laboratories. Two other glycopeptides known to be present in digests of human skin collagen, Gly-Phe-Hyl(Gal-Glc)-Gly-Ile-Arg and Gly-Pro-Hyl(Gal) were also isolated from digests of rat skin collagen. Three additional glycopeptides which had not been previously reported in other vertebrate collagens were purified and their structures analyzed. Two of them were hexapeptides, Gly-Phe-Hyl(Gal)-Gly-Ile-Arg and Gly-Pro-Hyl(Gal)-Gly-Glu-Leu, while the other was a tripeptide, Gly-Met-Hyl(Gal).
Characterization of the glycopeptides obtained from the purified
1 and
2 components of rat skin collagen and hexose analysis of the cyanogen bromide (CNBr) peptides derived from whole collagen as well as from both chains indicate the presence of only four major sites of glycosylation in the molecule. The evidence presented is consistent with the existence of an identical site in each
1 chain, corresponding to a disaccharide unit near the NH2 terminus of the
1-CB5 cyanogen bromide peptide. The other two sites are located in the CNBr peptide
2-CB4 derived from the
2 chain. There are, in addition, other minor sites of glycosylation in the molecule.
The limited number of sites of glycosylation and the location of all such sites in the same general area of the
chains near the NH2 terminus suggest a specific but unknown functional role in synthesis, fibril formation, or other basic aspects of collagen metabolism in skin.
Submitted on February 20, 1973