2-DIMENSIONAL NMR ASSIGNMENTS AND CONFORMATION OF (PRO-HYP-GLY)(10) AND A DESIGNED COLLAGEN TRIPLE-HELICAL PEPTIDE

Homonuclear and heteronuclear 2D NMR methods are used to study two tri ple-helical peptides. One peptide, (POG)10, is considered to be the mo st stable prototype of a triple helix. The second peptide, (POG)3ITGAR GLAGPOG(POG)3 (denoted T3-785), was designed to model an imino acid po or region of collagen and contains 12 residues from near the unique co llagenase cleavage site in type III collagen. Both peptides associated as trimers, with melting temperatures of 60-degrees-C for (POG)10 and 25-degrees-C for the T3-785 peptide. Sequence-specific assignments we re made for a tripeptide unit POG in (POG)10, and 80% of the POG tripl ets are found to be in an equivalent environment. In T3-785, with nonr epeating X-Y-Gly units incorporated in the sequence, the three chains of the homotrimer can be distinguished from one another by NMR. The so lution conformation of (POG)10 is very similar to the model derived fr om X-ray fiber diffraction data, although the peptide contains less or dered regions at the peptide ends. In the trimer form of T3-785, the c entral residues of the three chains are closely packed, and the data a re consistent with a triple-helical model with a one-residue stagger o f three parallel chains. For T3-785, in contrast to (POG)10, there are also resonances from a less ordered form, which are probably due to t he presence of a small amount of monomer. The similarity of the backbo ne conformations of T3-785 and (POG)10 suggests that an alternative co nformation is not present in the imino acid poor region.