title: Statistical radii associated with amino acids to determine the contact map: fixing the structure of a type I cohesin domain in the Clostridium thermocellum cellulosome.
abstract: We propose to improve and simplify protein refinement procedures through consideration of which pairs of amino acid residues should form native contacts. We first consider 11 330 proteins from the CATH database to determine statistical distributions of contacts associated with a given type of amino acid. The distributions are set across the distances between the α-C atoms that are in contact. Based on this data, we determine typical radii of effective spheres that can be placed on the α-C atoms in order to reconstruct the distribution of the contact lengths. This is done by checking for overlaps with enlarged van der Waals spheres associated with heavy atoms on other amino acids.The resulting contacts can be used to identify non-native contacts that may arise during the time evolution of structure-based models. Here, the radii are used to guide reconstruction of nine missing side chains in a type I cohesin domain with the Protein Data Bank code 1AOH. We first identify the likely missing contacts and then sculpt the corresponding side chains by standard refinement tools to achieve consistency with the expected contact map. One ambiguity in refinement is resolved by determining all-atom conformational energies.
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Chwastyk
authors.forename: Adolfo Poma
authors.initials: AP
authors.lastname: Bernaola
authors.forename: Marek
authors.initials: M
authors.lastname: Cieplak
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D018797:Cell Cycle Proteins / Q000737:chemistry*; D044603:Cellulosomes / Q000737:chemistry*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry*; D048013:Acetivibrio thermocellus / Q000737:chemistry*; D011487:Protein Conformation; D000097722:Cohesins
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D000097722:Cohesins