Characterization of hemin-binding protein 35

• Published in: BMC microbiology 2010-05, Vol.10, p.152
• Main Authors: Shoji, Mikio, Shibata, Yasuko, Shiroza, Teruaki, Yukitake, Hideharu, Peng, Benjamin, Chen, Yu-Yen, Sato, Keiko, Naito, Mariko, Abiko, Yoshimitsu, Reynolds, Eric C, Nakayama, Koji
• Format: Article
• Language: English
• Subjects: Anaerobic bacteria; Binding proteins; Growth; Physiological aspects
• ISSN: 1471-2180; 1471-2180
• DOI: 10.1186/1471-2180-10-152

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. 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. 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.