title: A direct-method ab initio phasing of a protein, cupredoxin amicyanin, at 1.31 A resolution.
abstract: The direct-methods program MULTAN88 has been applied successfully to redetermine the structure of a protein, cupredoxin amicyanin, containing 808 non-H atom sites, one Cu atom and 132 ordered water molecules in the asymmetric unit using data at 1.31 A resolution. Starting with initially random phases, useful phase sets selected by figures of merit could be obtained from multiple trials. The E maps corresponding to the best eight phase sets in order of combined figures of merit (CFOM2) revealed a distorted tetrahedral geometry around the Cu site. The phase estimates from the metal and a few neighbouring atoms in the initial E map corresponding to the set with the highest CFOM2 could be improved by the density-modification procedure PERP and led to an interpretable electron-density map.
authors.affiliation: Department of Solid State Physics, Indian Association for the Cultivation of Science, Calcutta-700032, India.
authors.forename: M
authors.initials: M
authors.lastname: Mukherjee
authors.forename: S
authors.initials: S
authors.lastname: Maiti
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: M M
authors.initials: MM
authors.lastname: Woolfson
mesh_terms: D001400:Azurin / Q000031:analogs & derivatives* / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010231:Paracoccus denitrificans / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; C050107:cupredoxin; C017079:mauC protein, Methylobacterium extorquens; D001400:Azurin