title: Crystal structure of alpha 1: implications for protein design.
abstract: X-ray diffraction shows the structure of a synthetic protein model, formed from noncovalent self-association of a 12-residue peptide and of sulfate ions at low pH. This peptide is a fragment of a 16-residue polypeptide that was designed to form an amphiphilic alpha helix with a ridge of Leu residues along one helical face. By interdigitation of the leucines of four such helices, the design called for self-association into a four-alpha-helical bundle. The crystal structure (2.7 angstrom resolution; R factor = 0.215) reveals a structure more complex than the design, with both a tetramer and a hexamer. The alpha-helical tetramer with leucine interior has more oblique crossing angles than most four-alpha-helical bundles; the hexamer has a globular hydrophobic core of 12 leucine residues and three associated sulfate ions. Computational analysis suggests that the hexameric association is tighter than the tetrameric one. The consistency of the structure with the design is discussed, as well as the divergence.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles 90024-1569.
authors.forename: C P
authors.initials: CP
authors.lastname: Hill
authors.forename: D H
authors.initials: DH
authors.lastname: Anderson
authors.forename: L
authors.initials: L
authors.lastname: Wesson
authors.forename: W F
authors.initials: WF
authors.lastname: DeGrado
authors.forename: D
authors.initials: D
authors.lastname: Eisenberg
mesh_terms: D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides; D011487:Protein Conformation; D011506:Proteins
chemical_list: D046911:Macromolecular Substances; D010455:Peptides; D011506:Proteins