title: A helix-turn-strand structural motif common in alpha-beta proteins.
abstract: By exhaustive structural comparisons, we have found that about one-third of the alpha-helix-turn-beta-strand polypeptides in alpha-beta barrel domains share a common structural motif. The chief characteristics of this motif are that first, the geometry of the turn between the alpha-helix and the beta-strand is somewhat constrained, and second, the beta-strand contains a hydrophobic patch that fits into a hydrophobic pocket on the alpha-helix. The geometry of the turn does not seem to be a major determinant of the alpha-beta unit, because the turns vary in length from four to six residues. However, the motif does not occur when there are few constraints on the geometry of the turn-for instance, when the turns between the alpha-helix and the beta-strands are very long. It also occurs much less frequently in flat-sheet alpha-beta proteins, where the topology is much less regular and the amount of twist on the sheet varies considerably more than in the barrel proteins. The motif may be one of the basic building blocks from which alpha-beta barrels are constructed.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
authors.forename: P A
authors.initials: PA
authors.lastname: Rice
authors.forename: A
authors.initials: A
authors.lastname: Goldman
authors.forename: T A
authors.initials: TA
authors.lastname: Steitz
mesh_terms: D000426:Alcohol Dehydrogenase / Q000648:ultrastructure; D000446:Aldehyde-Lyases; D000595:Amino Acid Sequence; D000681:Amylases / Q000648:ultrastructure; D002352:Carrier Proteins / Q000648:ultrastructure; D003196:Computer Graphics; D003198:Computer Simulation; D029968:Escherichia coli Proteins; D005418:Flavodoxin / Q000648:ultrastructure; D005980:Glutathione Reductase / Q000648:ultrastructure; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000648:ultrastructure; D019753:Intramolecular Lyases; D007535:Isomerases / Q000648:ultrastructure; D007770:L-Lactate Dehydrogenase / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010751:Phosphopyruvate Hydratase / Q000648:ultrastructure; D011487:Protein Conformation; D011770:Pyruvate Kinase / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D013884:Thiosulfate Sulfurtransferase / Q000648:ultrastructure; D014305:Triose-Phosphate Isomerase / Q000648:ultrastructure
chemical_list: C016242:AraF protein, E coli; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D005418:Flavodoxin; D000426:Alcohol Dehydrogenase; D007770:L-Lactate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D005980:Glutathione Reductase; D011770:Pyruvate Kinase; D013884:Thiosulfate Sulfurtransferase; D000681:Amylases; D000446:Aldehyde-Lyases; C100131:phospho-2-keto-3-deoxy-gluconate aldolase; D010751:Phosphopyruvate Hydratase; D007535:Isomerases; D014305:Triose-Phosphate Isomerase; D019753:Intramolecular Lyases; C021811:muconate cycloisomerase