Department of Macromolecular Science, Graduate School of Science, Osaka University^* Department of Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture and Technology^** Department of Biochemistry and Moloecular Biology, Oregon Health & Science University^***
○Tatsuya Kawaguchi^* Masaki Shimura^** Chizuru Hongo^* Keiichi Noguchi^** Kenji Okuyama^* Kazunori Mizuno^*** Hans Peter Bachinger^***

The crystal structure of the host-guest collagen model peptide, (Pro-Pro-Gly)4-Hyp-Asp-Gly-(Pro-Pro-Gly)4, was determined at 1.02Å resolution (R = 0.128, Rfree = 0.159) by using synchrotron radiation (PF BL6A). The crystal belongs to P21 space group with cell parameters of a = 31.59, b = 21.71, c = 39.15 Å, and b = 100.17°. The asymmetric unit contains one molecule which consists of three peptide strands and forms a collagen-like triple-helical structure. Although the helical twist of each residue ranges from 36° to 66°, the average values in the host (49.0°) and the guest (52.6°) parts agree very well with that for the ideal 7/2-helical model. Although Hyp residues in the X position of the (Hyp-Hyp-Gly)n (n=9, 10) were reported to adopt up-puckering, Hyp in the guest triplet of the present peptide adopts a down-puckering. The lateral packing structure of this peptide showed the quasi-hexagonal packing, which was usually observed for the Pro-Hyp-Gly sequence-rich peptides.
Two Asp residues in a triple helix were found to form hydrogen-bondings with Asp residues in the adjacent helices and the third Asp was found to interact electrostatically with N-terminal of the adjacent staggered molecule.