title: Features of the secondary structure of a protein molecule from powder diffraction data.
abstract: Protein powder diffraction is shown to be suitable for obtaining de novo solutions to the phase problem at low resolution via phasing methods such as the isomorphous replacement method. Two heavy-atom derivatives (a gadolinium derivative and a holmium derivative) of the tetragonal form of hen egg-white lysozyme were crystallized at room temperature. Using synchrotron radiation, high-quality powder patterns were collected in which pH-induced anisotropic lattice-parameter changes were exploited in order to reduce the challenging and powder-specific problem of overlapping reflections. The phasing power of two heavy-atom derivatives in a multiple isomorphous replacement analysis enabled molecular structural information to be obtained up to approximately 5.3 A resolution. At such a resolution, features of the secondary structure of the lysozyme molecule can be accurately located using programs dedicated to that effect. In addition, the quoted resolution is sufficient to determine the correct hand of the heavy-atom substructure which leads to an electron-density map representing the protein molecule of proper chirality.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Cristallographie, Lausanne, Switzerland. sebastian.basso@epfl.ch
authors.forename: Sebastian
authors.initials: S
authors.lastname: Basso
authors.forename: Céline
authors.initials: C
authors.lastname: Besnard
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Wright
authors.forename: Irene
authors.initials: I
authors.lastname: Margiolaki
authors.forename: Andrew
authors.initials: A
authors.lastname: Fitch
authors.forename: Philip
authors.initials: P
authors.lastname: Pattison
authors.forename: Marc
authors.initials: M
authors.lastname: Schiltz
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000737:chemistry*; D002645:Chickens; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D033362:Powder Diffraction; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D030161:Avian Proteins; D009113:Muramidase