title: Proline-rich salivary proteins have extended conformations.
abstract: Three basic proline-rich salivary proteins have been produced through the recombinant route. IB5 is a small basic proline-rich protein that is involved in the binding of plant tannins in the oral cavity. II-1 is a larger protein with a closely related backbone; it is glycosylated, and it is also able to bind plant tannins. II-1 ng has the same polypeptidic backbone as II-1, but it is not glycosylated. Small angle x-ray scattering experiments on dilute solutions of these proteins confirm that they are intrinsically disordered. IB5 and II-1 ng can be described through a chain model including a persistence length and cross section. The measured radii of gyration (Rg=27.9 and 41.0+/-1 A respectively) and largest distances (rmax=110 and 155+/-10 A respectively) show that their average conformations are rather extended. The length of the statistical segment (twice the persistence length) is b=30 A, which is larger than the usual value (18 A-20 A) for unstructured polypeptide chains. These characteristics are presumably related to the presence of polyproline helices within the polypeptidic backbones. For both proteins, the radius of gyration of the chain cross-section is Rc=2.7+/-0.2A. The glycosylated protein II-1 has similar conformations but the presence of large polyoside sidegroups yields the structure of a branched macromolecule with the same hydrophobic backbone and hydrophilic branches. It is proposed that the unusually extended conformations of these proteins in solution facilitate the capture of plant tannins in the oral cavity.
authors.affiliation: INRA, Montpellier SupAgro, UMR 1083 Sciences pour l'OEnologie, F-34060 Montpellier, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Boze
authors.forename: Thérèse
authors.initials: T
authors.lastname: Marlin
authors.forename: Dominique
authors.initials: D
authors.lastname: Durand
authors.forename: Javier
authors.initials: J
authors.lastname: Pérez
authors.forename: Aude
authors.initials: A
authors.lastname: Vernhet
authors.forename: Francis
authors.initials: F
authors.lastname: Canon
authors.forename: Pascale
authors.initials: P
authors.lastname: Sarni-Manchado
authors.forename: Véronique
authors.initials: V
authors.lastname: Cheynier
authors.forename: Bernard
authors.initials: B
authors.lastname: Cabane
mesh_terms: D000595:Amino Acid Sequence; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D006031:Glycosylation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D055273:Salivary Proline-Rich Proteins / Q000737:chemistry*; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D011994:Recombinant Proteins; D055273:Salivary Proline-Rich Proteins