ISOLATION AND CHARACTERIZATION OF A DISTINCT TYPE OF COLLAGEN FROM BOVINE FETAL MEMBRANES AND OTHER TISSUES

A new procedure has been developed to isolate a distinct bovine collagen fraction which contains αA and αB chains and resembles that reported by Burgeson et al. [Burgeson, R. E., El Adli, F. A., Kaitila, I. I., & Hollister, D. W. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 2579-2583], This fraction was obtained first from the bovine amnion and chorion, and the method was subsequently applied to the pepsin-solubilized collagens dissolved from cornea, tendon, skin, dura, nerve endoneurium, and cartilage. Electron microscopy reveals a single type of segment long-spacing crystallite, identical in staining characteristics with the “type VI” segments we previously distinguished among the collagens in bovine Descemet's membrane and heart valve. We were unable to separate the αA and αB chains on carboxy-methylcellulose but could resolve them by hydroxylapatite chromatography. The ratio of the aA to aB chains was 1:1.78. Amino acid analysis demonstrated that the compositions of the αA and αB chains are distinguishable and similar to analyses published for the homologous chains from human collagen. No cysteine or disulfide linkages were detected. Analysis of alkaline hydrolysates of both chains for sugar residues indicated that 84% of the hydroxylysines in αB and 45% in αA are glycosylated. The native collagen is apparently resistant to mammalian collagenase. We tentatively conclude that the αA and αB chains are both present in a native αA(αB)2 molecule because (1) when isolated from various tissues this collagen consistently contains the αA and αB chains in a ratio approximating 1:2, (2) only a single type of segment long-spacing aggregate could be detected by electron microscopy in these preparations, and (3) both chains are resistant to collagenase. © 1979, American Chemical Society. All rights reserved.