title: Two crystal modifications of (Pro-Pro-Gly)4-Hyp-Hyp-Gly-(Pro-Pro-Gly)4 reveal the puckering preference of Hyp(X) in the Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs in collagen helices.
abstract: Two crystal modifications of a collagen model peptide, (Pro-Pro-Gly)(4)-Hyp-Hyp-Gly-(Pro-Pro-Gly)(4) [where Hyp is (4R,2S)-L-hydroxyproline], showed very similar unit-cell parameters and belonged to the same space group P2(1). Both crystals exhibited pseudo-merohedral twinning. The main difference was in their molecular-packing arrangements. One modification showed pseudo-hexagonal packing, while the other showed pseudo-tetragonal packing. Despite their different packing arrangements, no significant differences were observed in the hydration states of these modifications. The peptide in the pseudo-tetragonal crystal showed a cyclic fluctuation of helical twists with a period of 20 A, while that in the pseudo-hexagonal crystal did not. In these modifications, the puckering conformations of four of the 12 Hyp residues at the X position of the Hyp(X)-Hyp(Y)-Gly sequence were in the opposite conformations to the previous hypothesis that Hyp(X) residues involved in Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs prefer up-puckering and down-puckering conformations, respectively. Detailed investigation of the molecular interactions between Hyp(X) and adjacent molecules revealed that these opposite conformations appeared because the puckering conformation, which follows the hypothesis, is subject to steric hindrance from the adjacent molecule.
authors.affiliation: Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. okuyamak@chem.sci.osaka-u.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Okuyama
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Morimoto
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Narita
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kawaguchi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Mizuno
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Bächinger
authors.forename: Guanghan
authors.initials: G
authors.lastname: Wu
authors.forename: Keiichi
authors.initials: K
authors.lastname: Noguchi
mesh_terms: D003094:Collagen / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D006909:Hydroxyproline / Q000737:chemistry* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D013237:Stereoisomerism
chemical_list: D046912:Multiprotein Complexes; D010446:Peptide Fragments; D003094:Collagen; D006909:Hydroxyproline