Porphyromonas gingivalis HmuY and HmuR: further characterization of a novel mechanism of heme utilization.
Porphyromonas gingivalis HmuY is a putative heme-binding lipoprotein associated with the outer membrane. It is part of an operon together with a gene encoding an outer-membrane hemin utilization receptor (HmuR) and four uncharacterized genes. A similar operon organization was found in Bacteroides fragilis and B. thetaiotaomicron, with the former containing an additional HmuY homologue encoded upstream of the hmuR-like gene. In P. gingivalis cultured under heme-limited conditions, a approximately 1-kb hmuY transcript was produced at high levels along with some approximately 3.5 and approximately 9-kb transcripts. Compared with the parental strain, mutants deficient in hmuY or hmuR or hmuY-hmuR gene function grew more slowly and bound lower amounts of hemin and hemoglobin. Significantly, they grew more slowly or were unable to grow when human serum was used as the sole iron/heme source. Analysis of the hmu promoter showed that it is regulated by iron. The HmuY protein normally occurs as a homodimer, but in the presence of hemin it may form tetramers. These results show that HmuY may be the first reported member of a new class of proteins in Porphyromonas and Bacteroides species involved in heme utilization, a function being exerted in conjunction with HmuR, an outer-membrane heme transporter.
Olczak
Teresa
T
Laboratory of Biochemistry, Faculty of Biotechnology, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland. Teresa.Olczak@biotech.uni.wroc.pl
Sroka
Aneta
A
Potempa
Jan
J
Olczak
Mariusz
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001439:Bacteroides / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D006418:Heme / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism; D006454:Hemoglobins; D006801:Humans; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D044967:Serum / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006454:Hemoglobins; D026901:Membrane Transport Proteins; D011956:Receptors, Cell Surface; C028027:heme receptor; D006418:Heme; D006427:Hemin