Procollagen biosynthesis and processing in guinea pig fibroblast culture medium

1. Collagen biosynthesis and processing by primary cultures (2nd subculture) of guinea pig embryo fibroblasts were studied. Collagen represents about 15% of the protein synthesized and extruded by these cells under the culture conditions employed. 2. After incubating the cells with [3H]-proline for varying periods of time, the labelled products from the cell layer and the medium were analyzed by polyacrylamide gel electrophoresis. 3. Fluorography of the corresponding gels showed that the cell layer contained only mature alpha 1 (I) and alpha 2 chains, while the medium contained five extra bands; four with mobilities between beta-dimers and alpha 1 (I), and one migrating between alpha 1 (I) and alpha 2. These molecules were identified as predominantly type-I collagen precursors and represent about 96% of the collagen synthesized by the fibroblasts. 4. Kinetic studies of procollagen processing after both short- and long-term labelling periods showed that removal of amino- and carboxy-terminal peptide extensions occurred independently.