Isolation and Characterization of Cyanogen Bromide‐Cleaved Peptides from a Collagenase Digest of α 1‐Chain of Calf Skin Collagen

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Abstract
Molecular fragments of various lengths are formed by treating acid‐soluble collagen with collagenase from Clostridium histolyticum. Fragments 78, 105 and 125 nm long can be isolated by fractional ammonium sulphate precipitation. Their position in the collagen molecule has been determined by electron optical investigations. Denaturation of the individual fragments yielded peptides of the α1‐ and α2‐chains which could be separated by CM‐cellulose chromatography.These peptides, α1 (78) and α1 (105), are in the region of two of those obtained by cyanogen bromide cleavage, namely, α1‐CB7 and CB6; α1 (125) is superimposed on α1‐CB3, CB7 and CB6. In order to obtain smaller fragments of these CB peptides of the α1‐chain, the three fragments from collagenase treatment were cleaved further with cyanogen bromide and the resultant peptides were isolated and characterized. Their position along the α1‐chain was determined electron microscopically after renaturation to the triple helical structure.Each fragment of the α1‐chain yields two chromatographically and electrophoretically distinguishable peptides which have been designated α1 and α1*. The difference between the two was found to reside in the –COOH end of the molecule: the α1* peptide contains seven amino acids more than the α1.