title: The 'Asx-Pro turn' as a local structural motif stabilized by alternative patterns of hydrogen bonds and a consensus-derived model of the sequence Asn-Pro-Asn.
abstract: Analyses of databases derived from the Brookhaven Protein Data Bank have identified a set of related turn structures formed by the sequence Asx-Pro-Xxx(n). In a variety of flanking structural contexts, more than 60% of Asx-Pro sequences adopt a turn conformation stabilized by a set of alternative hydrogen bonds among the side chain O delta and backbone C = O carbonyl oxygens of Asx (residue i) and the backbone NH of residues i + 2, i + 3 and in some cases i + 4. In contrast, the structures adopted by Ser-Pro, His-Pro and other Xxx-Pro sequences reflect more heterogeneous hydrogen-bonding patterns. As expected, structures formed by Asx-Pro-Asx are similar to those formed by Asx-Pro-Xxx(n), but in some cases additional hydrogen bonds are formed between the Asx side chains. Hydrogen bond patterns within Asx-Pro and Asn-Pro-Asn turns are consistent with published NMR studies of helical (Asn-Pro-Asn-Ala)n peptides, indicating that a consensus structure reflecting these hydrogen bonds can serve as a partial model of the Asn-Pro-Asn-Ala tetrapeptide repeats of Plasmodium falciparum circumsporozoite protein.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.
authors.forename: D R
authors.initials: DR
authors.lastname: Wilson
authors.forename: B B
authors.initials: BB
authors.lastname: Finlay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry; D001216:Asparagine / Q000737:chemistry*; D001224:Aspartic Acid / Q000737:chemistry*; D001665:Binding Sites; D016384:Consensus Sequence; D016208:Databases, Factual; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry
chemical_list: D000953:Antigens, Protozoan; D015800:Protozoan Proteins; C041595:circumsporozoite protein, Protozoan; D001224:Aspartic Acid; D001216:Asparagine; D011392:Proline