title: Characterization of hemin-binding protein 35 (HBP35) in Porphyromonas gingivalis: its cellular distribution, thioredoxin activity and role in heme utilization.
abstract: BACKGROUND
  The periodontal pathogen Porphyromonas gingivalis is an obligate anaerobe that requires heme for growth. To understand its heme acquisition mechanism, we focused on a hemin-binding protein (HBP35 protein), possessing one thioredoxin-like motif and a conserved C-terminal domain, which are proposed to be involved in redox regulation and cell surface attachment, respectively.
  
  
  RESULTS
  We observed that the hbp35 gene was transcribed as a 1.1-kb mRNA with subsequent translation resulting in three proteins with molecular masses of 40, 29 and 27 kDa in the cytoplasm, and one modified form of the 40-kDa protein on the cell surface. A recombinant 40-kDa HBP35 exhibited thioredoxin activity in vitro and mutation of the two putative active site cysteine residues abolished this activity. Both recombinant 40- and 27-kDa proteins had the ability to bind hemin, and growth of an hbp35 deletion mutant was substantially retarded under hemin-depleted conditions compared with growth of the wild type under the same conditions.
  
  
  CONCLUSIONS
  P. gingivalis HBP35 exhibits thioredoxin and hemin-binding activities and is essential for growth in hemin-depleted conditions suggesting that the protein plays a significant role in hemin acquisition.
authors.affiliation: Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Mikio
authors.initials: M
authors.lastname: Shoji
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Shibata
authors.forename: Teruaki
authors.initials: T
authors.lastname: Shiroza
authors.forename: Hideharu
authors.initials: H
authors.lastname: Yukitake
authors.forename: Benjamin
authors.initials: B
authors.lastname: Peng
authors.forename: Yu-Yen
authors.initials: YY
authors.lastname: Chen
authors.forename: Keiko
authors.initials: K
authors.lastname: Sato
authors.forename: Mariko
authors.initials: M
authors.lastname: Naito
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Abiko
authors.forename: Eric C
authors.initials: EC
authors.lastname: Reynolds
authors.forename: Koji
authors.initials: K
authors.lastname: Nakayama
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D000081062:Heme-Binding Proteins; D006420:Hemeproteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D050505:Mutant Proteins / Q000378:metabolism; D016966:Porphyromonas gingivalis / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011485:Protein Binding; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D013879:Thioredoxins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D050505:Mutant Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D013879:Thioredoxins; D006427:Hemin