title: HmuS from Yersinia pseudotuberculosis is a non-canonical heme-degrading enzyme to acquire iron from heme.
abstract: Some Gram-negative pathogens import host heme into the cytoplasm and utilize it as an iron source for their survival. We report here that HmuS, encoded by the heme utilizing system (hmu) locus, cleaves the protoporphyrin ring to release iron from heme. A liquid chromatography/mass spectrometry analysis revealed that the degradation products of this reaction are two biliverdin isomers that result from transformation of a verdoheme intermediate. This oxidative heme degradation by HmuS required molecular oxygen and electrons supplied by either ascorbate or NADPH. Electrons could not be directly transferred from NADPH to heme; instead, ferredoxin-NADP+reductase (FNR) functioned as a mediator. Although HmuS does not share amino acid sequence homology with heme oxygenase (HO), a well-known heme-degrading enzyme, absorption and resonance Raman spectral analyses suggest that the heme iron is coordinated with an axial histidine residue and a water molecule in both enzymes. The substitution of axial His196 or distal Arg102 with an alanine residue in HmuS almost completely eliminated heme-degradation activity, suggesting that Fe-His coordination and interaction of a distal residue with water molecules in the heme pocket are important for this activity.
authors.affiliation: Department of Biological Chemistry, Graduate School of Science and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Onzuka
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Sekine
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uchida
authors.affiliation: Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ishimori
authors.affiliation: Department of Biological Chemistry, Graduate School of Science and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan. Electronic address: ozakis@yamaguchi-u.ac.jp.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Ozaki
mesh_terms: D005287:Ferredoxin-NADP Reductase / Q000378:metabolism; D006418:Heme / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship; D015011:Yersinia pseudotuberculosis / Q000201:enzymology*
chemical_list: D006418:Heme; D009249:NADP; D007501:Iron; D005287:Ferredoxin-NADP Reductase
keywords: Biliverdin; Ferredoxin; Ferredoxin-NADP(+) reductase; Heme; Iron; Yersinia pseudotuberculosis