title: Structural basis for multimeric heme complexation through a specific protein-heme interaction: the case of the third neat domain of IsdH from Staphylococcus aureus.
abstract: To elucidate the heme acquisition system in pathogenic bacteria, we investigated the heme-binding properties of the third NEAT domain of IsdH (IsdH-NEAT3), a receptor for heme located on the surfaces of pathogenic bacterial cells, by using x-ray crystallography, isothermal titration calorimetry, examination of absorbance spectra, mutation analysis, size-exclusion chromatography, and analytical ultracentrifugation. We found the following: 1) IsdH-NEAT3 can bind with multiple heme molecules by two modes; 2) heme was bound at the surface of IsdH-NEAT3; 3) candidate residues proposed from the crystal structure were not essential for binding with heme; and 4) IsdH-NEAT3 was associated into a multimeric heme complex by the addition of excess heme. From these observations, we propose a heme-binding mechanism for IsdH-NEAT3 that involves multimerization and discuss the biological importance of this mechanism.
authors.affiliation: Department of Medical Genome Sciences, Graduate School of Frontier Sciences, the University of Tokyo, Tokyo 277-8562, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Ayuko
authors.initials: A
authors.lastname: Suenaga
authors.forename: Makoto
authors.initials: M
authors.lastname: Kuroda
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Watanabe
authors.forename: Fumio
authors.initials: F
authors.lastname: Arisaka
authors.forename: Toshiko
authors.initials: T
authors.lastname: Ohta
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry*; D002151:Calorimetry; D002462:Cell Membrane / Q000378:metabolism; D018360:Crystallography, X-Ray / Q000379:methods; D004252:DNA Mutational Analysis; D005822:Genetic Vectors; D006418:Heme / Q000737:chemistry*; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface; D013211:Staphylococcus aureus / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D000942:Antigens, Bacterial; C512792:IsdH protein, Staphylococcus aureus; D011956:Receptors, Cell Surface; D006418:Heme