Analysis of a crosslinked peptide from calf bone collagen: evidence that hydroxylysyl glycoside participates in the crosslink

A crosslinked, double-chained peptide has been isolated from calf bone collagen after digestion with crude bacterial collagenase. Initially, the ³H-labelled peptide was isolated from collagen that had been treated with ³H]-NaBH₄, but an almost identical peptide was also isolated from collagen without prior reduction. After periodate oxidation of the reduced peptide the two component chains were resolved by further chromatography. Amino acid compositions showed that the peptide probably derived from an intermolecular crosslink between a carboxyterminal sequence of the collagen molecule and a sequence near the aminoterminus that previously has been shown to be the site of a glycosylated hydroxylysine residue. The crosslinking compound in the reduced peptide, hydroxylysinohydroxynorleucine, appeared to have derived mainly by reduction with borohydride of hydroxylysinooxonorleucine, the keto-amine rearranged form of the dehydro crosslink. The remaining hydroxyl group of the crosslink, the one not derived by reduction of the keto group, appeared to be glycosylated.