Fig. 2. The α2(I) C-propeptides can be cross-linked to PDI in a non-thiol-dependent manner. RNA coding for the α2(I), the α1(III) and the S3 C-propeptides were translated in a rabbit reticulocyte lysate in the presence of SP cells. SP cells were isolated by centrifugation and translation products were left untreated (lanes 1, 3 and 5) or chemically cross-linked with DSP (lanes 2, 4 and 6). Cross-linked samples were immunoprecipitated using the indicated antibodies before separation by SDS–PAGE on a 10% polyacrylamide gel, and were visualized by autoradiography.