A unique, pepsin-sensitive collagen synthesized by aortic endothelial cells in culture

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Abstract
A unique collagen, designated EC, was isolated from the culture medium of adult bovine aortic endothelial cells. After diethylaminoethylcellulose chromatography of [3H]proline-labeled culture medium, 3 non-disulfide-bonded bacterial collagenase-sensitive components with apparent MW of 177,000 (EC 1), 125,000 (EC 2) and 100,000 (EC 3) were demonstrated. Molecular sieve chromatography, cyanogen bromide cleavage and 2-dimensional peptide mapping of radioiodinated EC fragments produced by protease digestion suggest that the lower MW components originate from EC 1. EC 1 and EC 2 were digested by pepsin within 10 min to products of < 60,000 MW under conditions which supported limited proteolysis of other native colagens. A pepsin-resistant fragment of MW 50,000 derived from a digest of EC 2 contained equal amounts of hydroxyproline and proline; at least a portion of the endothelial collagen apparently contains a stable, collagen-like triple helix. Comparative mapping using mast cell protease and cyanogen bromide cleavage, followed by polyacrylamide gel electrophoresis, indicates that the primary structure of this collagen differs from that of other known collagen types.