Sweet is stable: glycosylation stabilizes collagen.

For most collagens, the melting temperature (T(m)) of the triple-helical structure 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-Yaa- triplet repeat. The cuticle collagen of the deep-sea hydrothermal vent worm Riftia pachyptila, despite a very low content of Pro and Hyp, has a relatively 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 forming propensities in water of two model peptides, Ac-(Gly-Pro-Thr)(10)-NH(2) and Ac-(Gly-Pro-Thr(Galbeta))(10)-NH(2), and show that a collagen triple-helix structure is only achieved after glycosylation of Thr. Thus, we show for the first time that glycosylation is required for the formation of a stable tertiary structure and that this modification represents an alternative way of stabilizing the collagen triple-helix that is independent of the presence of Hyp.