Sweet is stable: glycosylation stabilizes collagen

For most collagens, the melting temperature (T-m) of the triple-helical str ucture of collagen correlates with the total content of proline (Pro) and 4 -trans-hydroxyproline (Hyp) in the Xaa and Yaa positions of the -Gly-Xaa-Ya a- triplet repeat. The cuticle collagen of the deep-sea hydrothermal vent w orm Riftia pachyptila, despite a very low content of Pro and Hyp, has a rel atively high thermal stability. Rather than Hyp occupying the Yaa position, as is normally found in mammalian collagens, this position is occupied by threonine (Thr) which is O-glycosylated, We compare the triple-helix formin g propensities in water of two model peptides, Ac(Gly-Pro-Thr)(10)-NH2 and Ac-(Gly-ProThr(Gal beta))(10)-NH2, and show that a collagen triple-helix st ructure is only achieved after glycosylation of Thr, Thus, we show for the first time that glycosylation is required for the formation of a stable ter tiary structure and that this modification represents an alternative way of stabilizing the collagen triple-helix that is independent of the presence of Hyp. (C) 2000 Federation of European Biochemical Societies.