Synthesis of heterotrimeric collagen models containing Arg residues in Y-positions and analysis of their conformational stability.

An Arg residue incorporated into the Y-position of collagenous host-guest peptide Ac-(Gly-Pro-Hyp)(3)-Gly-Pro-Y-(Gly-Pro-Hyp)(4)-Gly-Gly-NH(2) is reported to stabilize the triple helical structure as well as a 4(R)-hydroxyproline (Hyp) residue. Here, we synthesized heterotrimeric collagen models containing Arg in Y-positions utilizing the cystine knot strategy. Analysis of their thermal transition temperatures using circular dichroism spectrometry demonstrated unexpected decrease in the triple helical stability as the number of Arg increased. The obtained results indicated that an Arg residue in a Y-position is not always an equivalent of a Hyp residue, and that it possesses a potential helix destabilizing effect.