Functional identification of HugZ, a heme oxygenase from Helicobacter pylori.
BACKGROUND
Iron is recognized as an important trace element, essential for most organisms including pathogenic bacteria. HugZ, a protein related to heme iron utilization, is involved in bacterial acquisition of iron from the host. We previously observed that a hugZ homologue is correlated with the adaptive colonization of Helicobacter pylori (H. pylori), a major gastro-enteric pathogen. However, its exact physiological role remains unclear.


RESULTS
A gene homologous to hugZ, designated hp0318, identified in H. pylori ATCC 26695, exhibits 66% similarity to cj1613c of Campylobacter jejuni NCTC 11168. Soluble 6 x His fused-HugZ protein was expressed in vitro. Hemin-agrose affinity analysis indicated that the recombinant HugZ protein can bind to hemin. Absorption spectroscopy at 411 nm further revealed a heme:HugZ binding ratio of 1:1. Enzymatic assays showed that purified recombinant HugZ protein can degrade hemin into biliverdin and carbon monoxide in the presence of either ascorbic acid or NADPH and cytochrome P450 reductase. The biochemical and enzymatic characteristics agreed closely with those of Campylobacter jejuni Cj1613c protein, implying that hp0318 is a functional member of the HugZ family. A hugZ deletion mutant was obtained by homologous recombination. This mutant strain showed poor growth when hemoglobin was provided as the source of iron, partly because of its failure to utilize hemoglobin efficiently. Real-time quantitative PCR also confirmed that the expression of hugZ was regulated by iron levels.


CONCLUSIONS
These findings provide biochemical and genetic evidence that hugZ (hp0318) encodes a heme oxygenase involved in iron release/uptake in H. pylori.
Guo
Ying
Y
Department of Clinical Microbiology and Immunology, College of Medical Laboratory, Third Military Medical University, Chongqing, PR China. eaglegying@gmail.com
Guo
Gang
G
Mao
Xuhu
X
Zhang
Weijun
W
Xiao
Jie
J
Tong
Wende
W
Liu
Tao
T
Xiao
Bin
B
Liu
Xiaofei
X
Feng
Youjun
Y
Zou
Quanming
Q
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D006418:Heme / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006427:Hemin / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D006418:Heme; D006427:Hemin; D007501:Iron; D006419:Heme Oxygenase (Decyclizing)