title: Structure of methemerythrin at 2.8-Angstrom resolution: computer graphics fit of an averaged electron density map.
abstract: The crystal structure of methemerythrin from Themiste dyscritum has been determined at 2.8-Angstrom resolution by single isomorphous replacement technique combined with anomalous scattering from a K2HgI4 derivative. Noncrystallographic symmetry relating the four subunits in the asymmetric unit was used to obtain an average electron density map of the hemerythrin monomer, and a computer graphics system was used to fit a polypeptide model to the electron density. The average map was of sufficient quality to locate most of the amino acid side chains and to confirm the assignment of His-25, His-54, Glu-58, His-73, His-77, His-101, Asp-106, and Tyr-109 as the iron ligands. One of the mercury sites in the heavy atom derivative is located between two Cys-9 residues related by a noncrystallographic twofold axis, although no intersubunit disulfide bond is present in the native structure. The residues responsible for the binding of the subunits to form the octamer are identified.
mesh_terms: D000596:Amino Acids; D000818:Animals; D003201:Computers; D004583:Electrons; D006422:Hemerythrin; D007448:Invertebrates; D007501:Iron; D008667:Metalloproteins; D008958:Models, Molecular; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D000596:Amino Acids; D006422:Hemerythrin; D008667:Metalloproteins; D007501:Iron