Conformational Preference of Polyglycine in Solution to Elongated Structure

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• 作者：Satoshi Ohnishi ; Hironari Kamikubo ; Masayoshi Onitsuka ; Mikio Kataoka ; David Shortle
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：December 20, 2006
• 年：2006
• 卷：128
• 期：50
• 页码：16338 - 16344
• 全文大小：228K
• 年卷期：v.128,no.50(December 20, 2006)
• ISSN：1520-5126

文摘

Do polypeptide chains ever behave like a random coil? In this report we demonstrate that glycine,the residue with the fewest backbone restrictions, exhibits a strong preference for an extended conformationin solution when polymerized in short segments of polyglycine. A model peptide system comprised of twounique tripeptide units, between which 1 to 18 glycine residues are inserted, is characterized by NMR andby small-angle X-ray scattering (SAXS). The residual dipolar coupling (RDC) values of the two tripeptideunits are insensitive to changes in number of intervening glycines, suggesting that extension of the linkerdoes not alter the average angular relationship between the tripeptides. Polyglycine segments longer thannine residues form insoluble aggregates. SAXS measurements using synchrotron radiation provide directevidence that polyglycine peptides adopt elongated conformations. In particular, the construct with a linkerwith six glycines showed a scattering profile indicative of a monomeric state with a radius of gyration andthe maximum dimension of 9.1 Å and ~34 Å, respectively. The ensemble averaged global structure of this12-mer peptide can best be approximated by a cylinder with a radius of 4 Å and a length of ~33 Å, makingit intermediate in extension between a strand and an helix.