Glycosylation/hydroxylation-induced stabilization of the collagen triple helix -: 4-trans-hydroxyproline in the Xaa position can stabilize the triple helix

We have shown recently that glycosylation of threonine in the peptide Ac-(Gly-Pro-Thr)(10)-NH2 with beta-D-galactose induces the formation of a collagen triple helix, whereas the nonglycosylated peptide does not. In this report, we present evidence that a collagen triple helix can also be formed in the Ac-(Gly-Pro-Thr)(10)-NH2 peptide, if the proline (Pro) in the Xaa position is replaced with 4-transhydroxyproline (Hyp). Furthermore, replacement of Pro with Hyp in the sequence Ac-(Gly-Pro-Thr(beta-D-Gal))(10)-NH2 increases the T-m of the triple helix by 15.7 degrees C, It is generally believed that Hyp in the Xaa position destabilizes the triple helix because (Pro-Pro-Gly)(10) and (Pro-Hyp-Gly)(10) farm stable triple helices but the peptide (Hyp-Pro-Gly)(10) does not. Our data suggest that the destabilizing effect of Hyp relative to Pro in the Xaa position is only true in the case of (Hyp-Pro-Gly)(10), Increasing concentrations of galactose in the solvent stabilize the triple helix of Ac-(Gly-Hyp-Thr)(10)-NH2 but to a much lesser extent than that achieved by covalently linked galactose. The data explain some of the forces governing the stability of the annelid/vestimentiferan cuticle collagens.