Heme transporter playing an important role in stationary-phase iron acquisition and required for maintenance of chronic infection in mice. Induced in absence of iron. Maximally expressed during stationary phase when cultivated in low-iron minimal medium. The mutant is unable to use hemin as an iron source but retains the ability to use ferric chloride and the siderophore 2,3-DHBA. Exhibits an accelerated loss of viability after 144 hours of culture in low-iron minimal medium. Exhibits significant attenuation in murine macrophages and is unable to maintain a chronic spleen infection in mice. Belongs to the TonB-dependent receptor family.