title: Identification of an Escherichia coli O157:H7 heme oxygenase with tandem functional repeats.
abstract: Heme oxygenases (HOs) catalyze the oxidation of heme to biliverdin, carbon monoxide (CO), and free iron. Iron acquisition is critical for invading microorganisms to enable survival and growth. Here we report the crystal structure of ChuS, which displays a previously uncharacterized fold and is unique compared with other characterized HOs. Despite only 19% sequence identity between the N- and C-terminal halves, these segments of ChuS represent a structural duplication, with a root-mean-square deviation of 2.1 A between the two repeats. ChuS is capable of using ascorbic acid or cytochrome P450 reductase-NADPH as electron sources for heme oxygenation. CO detection confirmed that ChuS is a HO, and we have identified it in pathogenic Escherichia coli O157:H7. Based on sequence analysis, this HO is present in many bacteria, although not in the E. coli K-12 strain. The N- and C-terminal halves of ChuS are each a functional HO.
authors.affiliation: Departments of Biochemistry and Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Michael D L
authors.initials: MD
authors.lastname: Suits
authors.forename: Gour P
authors.initials: GP
authors.lastname: Pal
authors.forename: Kanji
authors.initials: K
authors.lastname: Nakatsu
authors.forename: Allan
authors.initials: A
authors.lastname: Matte
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Cygler
authors.forename: Zongchao
authors.initials: Z
authors.lastname: Jia
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism; D018360:Crystallography, X-Ray; D019453:Escherichia coli O157 / Q000201:enzymology*; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008665:Metalloporphyrins / Q000494:pharmacology; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry; D020080:Tandem Repeat Sequences
chemical_list: D008665:Metalloporphyrins; C055421:tin mesoporphyrin; D006418:Heme; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing)