title: Cj1386, an atypical hemin-binding protein, mediates hemin trafficking to KatA in Campylobacter jejuni.
abstract: Catalase enzymes detoxify H2O2 by the dismutation of H2O2 into O2 and H2O through the use of hemin cofactors. While the structure and biochemical properties of catalase enzymes have been well characterized over many decades of research, it remained unclear how catalases acquire hemin. We have previously reported that Cj1386 is essential for ensuring proper hemin content in Campylobacter jejuni catalase (KatA) (A. Flint, Y. Q. Sun, and A. Stintzi, J Bacteriol 194: 334-345, 2012). In this report, an in-depth molecular characterization of Cj1386 was performed to elucidate the mechanistic details of this association. Coimmunoprecipitation assays revealed that KatA-Cj1386 transiently interact in vivo, and UV-visible spectroscopy demonstrated that purified Cj1386 protein binds hemin. Furthermore, hemin titration experiments determined that hemin binds to Cj1386 in a 1:1 ratio with hexacoordinate hemin binding. Mutagenesis of potential hemin-coordinating residues in Cj1386 showed that tyrosine 57 was essential for hemin coordination when Cj1386 was overexpressed in Escherichia coli. The importance of tyrosine 57 in hemin trafficking in vivo was confirmed by introducing the cj1386(Y57A) allele into a C. jejuni Δcj1386 mutant background. The cj1386(Y57A) mutation resulted in increased sensitivity toward H2O2 relative to the wild type, suggesting that KatA was not functional in this strain. In support of this finding, KatA immunoprecipitated from the Δcj1386+cj1386(Y57A) mutant had significantly reduced hemin content compared to that of the cj1386(WT) background. Overall, these findings indicate that Cj1386 is involved in directly trafficking hemin to KatA and that tyrosine 57 plays a key role in this function.
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Annika
authors.initials: A
authors.lastname: Flint
authors.affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada astintzi@uottawa.ca.
authors.forename: Alain
authors.initials: A
authors.lastname: Stintzi
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001692:Biological Transport; D016123:Campylobacter jejuni / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism*; D008969:Molecular Sequence Data; D016415:Sequence Alignment
chemical_list: D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D006427:Hemin; D002374:Catalase