Non-disulfided pro alpha(1)(IV) chain in B16 melanoma cell culture

We have previously reported that two species of pro alpha(1)(IV) collagen chains, disulfided (500 kDa) and non-disulfided (180 kDa), were produced by B16 melanoma cells (J Biochem (1994) 116; 1039-1043). The mechanism by which the non-disulfided pro alpha(1)(IV) chain is produced was studied. No significant difference in prolyl hydroxylation in both polypeptides was observed. When the culture was treated with alpha,alpha'dipyridyl, a potent inhibitor for hydroxylation of collagen, the secretion of the disulfided alpha(1)(IV) chain was inhibited, but non-disulfided alpha(1)(IV) chain secretion was not affected. Short pulse and pulse-chase experiments demonstrated that both chains appeared at the same time in the culture medium and the relative amounts of both chains in the medium were unaltered with increasing chase periods. These results indicate that the non-disulfided alpha(1)(IV) chain is fully hydroxylated and that it's secretion is independent of it's hydroxylation level. A marked susceptibility of the 180 kDa alpha(1)(IV) chain to pepsin at 4 degrees C suggests that the non-disulfided chain may be present in a denatured form.