title: On residues in the disallowed region of the Ramachandran map.
abstract: An analysis of the occurrence of nonglycyl residues in conformations disallowed in the Ramachandran plot is presented. Ser, Asn, Thr, and Cys have the highest propensities to exhibit such conformations, and the branched aliphatic residues the lowest. Residues cluster in five regions and there are some trends in the types of residues and their side-chain conformations (chi(1)) occupying these. Majority of the residues are found at the edge of helices and strands and in short loops, and are involved in different types of weak, stabilizing interactions. A structural motif has been identified where a residue in disallowed conformation occurs as the first residue of a short 3(10)-helix. On the basis of the types of neighboring residues, the location in the three-dimensional structure and accessibility, there are similarities with the occurrence of cis peptide bonds in protein structures.
authors.affiliation: Department of Biochemistry, Bose Institute, P-1/12 CIT Scheme VIIM, Calcutta 700 054, India.
authors.forename: Debnath
authors.initials: D
authors.lastname: Pal
authors.forename: Pinak
authors.initials: P
authors.lastname: Chakrabarti
mesh_terms: D000465:Algorithms; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry*; D016000:Cluster Analysis; D030562:Databases, Protein; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D014102:Torsion Abnormality
chemical_list: D000596:Amino Acids; D011506:Proteins