Alteration in the conformational stability of collagen caused by the incorporation of the lysine analogue S-2-aminoethylcysteine

We studied the effects of the lysine analogue S-2-aminoethylcysteine on the activation of lysyl tRNA and on the secretion and conformational stability of newly synthesized type I collagen in embryonic chick tendon fibroblasts. The analogue competed efficiently with lysine for activation onto tRNA without affecting significantly the activation of other amino acids (K-m for lysine: 1.6 mu M; K-i for S-2-aminoethylcysteine: 1.4 mu M). The analogue also profoundly inhibited the synthesis and secretion of [C-14]procollagen but did not affect the synthesis or secretion of non-collagenous proteins. Although the [C-14]proline-labeled procollagen synthesized in the presence of S-2-aminoethylcysteine contained normal levels of hydroxyproline, it was susceptible to digestion with pepsin at 25 degrees C, indicating that incorporation of the analogue altered the conformational stability of the collagen triple helix. This analogue should be a powerful tool to further study the role of lysine on collagen structure and to determine how altered collagen structure affects its synthesis and secretion. Furthermore, this analogue may be a potent and selective inhibitor of collagen accumulation in pathologic conditions accompanied by tissue fibrosis.