Printed in Great Britain 433 Hydroxylysine in the N - Terminal Regions of the al - and c 2 - Chains of Various Collagens

The degree of hydroxylation of the lysine residue located in both ocland C2chains of collagen in the N-terminal, non-helical telopeptide region of the molecule has been determined in collagen from various sources after isolation of the peptides (aland ex2-CBI) that contain the lysine residue in question and are obtained by cyanogen bromide cleavage of collagen acland X2-chains respectively. As with collagen from chick tibia, bone collagens from rat tibia and femur and embryonic chick frontal bone, have a high degree of hydroxylation (approx. 50% or more) of the lysine residue in both oland a2-CBl peptides. This is in contrast with the lack of hydroxylation of this residue in both cxland ac2-chains of all skin collagens so far examined. The presence of hydroxylysine in ac Iand OC2-CB1 peptides from tendon collagen is also indicated. In rat tail tendon collagen the amount of hydroxylation is only slight but in the much less soluble tendon collagen from embryonic chick leg tendons, approximately one-third of the lysine is hydroxylated.