title: Direct phasing at low resolution of a protein copurified with human paraoxonase (PON1).
abstract: In this paper, the low-resolution structure of a previously unknown protein copurified with human paraoxonase (PON1) is reported. The structure of this protein was very difficult to solve using classical crystallographic methods. Progress was made using a new phasing method based on topological analysis. From the experimental point of view, this method has the advantage of requiring only a simple low-resolution X-ray data set. The program used and the different steps of the data-processing and phasing procedure are described. The results provided an insight into the failure of previous molecular-replacement attempts. The low-resolution shape of the protein which was presented with confidence is compared with and confirmed by the structure at 1.8 A solved subsequently using classical methods. This work shows that this direct-phasing method could be used systematically in difficult cases: it provides low-resolution structural information comparable with that obtainable by electron microscopy.
authors.affiliation: Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques, Unité Mixte de Recherche 7036 CNRS, Université Henri Poincaré Nancy I, BP 239, 54506 Vandoeuvre-lès-Nancy, France.
authors.forename: A
authors.initials: A
authors.lastname: Fokine
authors.forename: R
authors.initials: R
authors.lastname: Morales
authors.forename: C
authors.initials: C
authors.lastname: Contreras-Martel
authors.forename: P
authors.initials: P
authors.lastname: Carpentier
authors.forename: F
authors.initials: F
authors.lastname: Renault
authors.forename: D
authors.initials: D
authors.lastname: Rochu
authors.forename: E
authors.initials: E
authors.lastname: Chabriere
mesh_terms: D043303:Aryldialkylphosphatase / Q000097:blood / Q000737:chemistry* / Q000302:isolation & purification; D001798:Blood Proteins / Q000737:chemistry* / Q000302:isolation & purification; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods*; D005583:Fourier Analysis; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D001798:Blood Proteins; D043303:Aryldialkylphosphatase