X-RAY CRYSTALLOGRAPHIC STUDIES OF COLLAGEN-LIKE PEPTIDES. Rachel Kramer¹, Jinsong Liu¹, Jordi Bella³, Manju Venugopal², Patricia Mayville¹, Barbara Brodsky², Helen M. Berman¹. ¹Department of Chemistry, Rutgers University, Piscataway NJ 08855, ²Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Piscataway NJ 08855, and ³Present address: Department of Biological Sciences, Purdue University, West Lafayette IN 47907.

Peptide models have proved extremely useful in the elucidation of the structure of collagen and the triple-helical motif. We have crystallized three new triple-helical peptides and will report the results of the structural analyses of these collagen-like peptides. One of these peptides is a homotrimer in which 12 residues from human type III collagen are embedded. This imino acid-poor region is located near the unique collagenase cleavage site and contains a glycine residue known to be the site of a lethal Gly->Ser mutation. This structure could potentially help resolve issues of interchain hydrogen bonding in imino acid-poor regions. Another of the peptides is missing a hydroxyproline at the center of the triple helix, therby interrupting the repeating Gly-X-Y pattern. This omission models a type of break that occurs frequently in nonfibrillar collagens and is found to a lesser extent in noncollagenous triple-helical proteins, such as C1q and mannose binding protein. It is possible that such interruptions may be important to molecular structure or supramolecular association. A third peptide containing lysine and glutamic acid was synthesized to examine the effect of a pair of adjacent charged residues on a triple helix and the role electrostatic interactions play in triple-helical conformation.

Research supported by NIH grants GM21589, AR19626 and a Molecular Biophysics Training Grant.