title: Cocrystals of yeast cytochrome c peroxidase and horse heart cytochrome c.
abstract: Yeast cytochrome c peroxidase and horse heart cytochrome c have been cocrystallized in a form suitable for x-ray diffraction studies and the structure determined at 3.3 A. The asymmetric unit contains a dimer of the peroxidase which was oriented and positioned in the unit cell using molecular replacement techniques. Similar attempts to locate the cytochrome c molecules were unsuccessful. The peroxidase dimer model was subjected to eight rounds of restrained parameters least squares refinement after which the crystallographic R factor was 0.27 at 3.3 A. Examination of a 2Fo-Fc electron density map showed large "empty" regions between peroxidase dimers with no indication of cytochrome c molecules. Electrophoretic analysis of the crystals demonstrated the presence of the peroxidase and cytochrome c in an approximate equal molar ratio. Therefore, while cytochrome c molecules are present in the unit cell they are orientationally disordered and occupy the space between peroxidase dimers.
authors.affiliation: Protein Engineering Department, Genex Corporation, Gaithersburg, Maryland 20877.
authors.forename: T L
authors.initials: TL
authors.lastname: Poulos
authors.forename: S
authors.initials: S
authors.lastname: Sheriff
authors.forename: A J
authors.initials: AJ
authors.lastname: Howard
mesh_terms: D000818:Animals; D003460:Crystallization; D003574:Cytochrome c Group / Q000302:isolation & purification / Q000378:metabolism*; D003578:Cytochrome-c Peroxidase / Q000302:isolation & purification / Q000378:metabolism*; D006736:Horses; D008958:Models, Molecular; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D010544:Peroxidases / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D014961:X-Ray Diffraction
chemical_list: D003574:Cytochrome c Group; D010544:Peroxidases; D003578:Cytochrome-c Peroxidase