A Study on the Conversion of Procollagen

Abstract

Abstract An in vitro study of the conversion of procollagen to collagen was carried out by culturing embryonic chicken calvaria and labeling them with [3,4-3H]proline and [35S]cysteine. A pulse experiment in the presence of α,α'-dipyridyl, an iron chelator, was used to accumulate procollagen in the tissue. The presence of procollagen was demonstrated by the incorporation of [35S]cysteine and by its chromatographic behavior on CM-cellulose under denaturing conditions. Using a parallel sample for a subsequent chase experiment in the absence of α,α'-dipyridyl, only traces of procollagen were found in the tissue, since [35S]cysteine had disappeared and radioactive material chromatographed with the authentic α chains of lathyritic rat skin collagen. It is proposed that the conversion of procollagen to collagen is paralleled by the release of procollagen peptides into the culture medium, indicating a single step enzymatic cleavage. These peptides were isolated from the culture medium, and their molecular weights were determined as 18,000 for a [35S]cysteine-containing and 12,000 for a [35S]cysteine-free peptide. Both values are within the size range expected for peptides cleaved from procollagen chains of molecular weights between 110,000 and 120,000.