FIGURE 8.

A model showing how heme is transported into L. monocytogenes. The majority of Hbp2 is secreted and binds Hb but may also bind Hb on the surface via Hbp2 or Hbp1. The dotted lines represent our observation that Hbp2 is also secreted. Heme can be transferred to cell wall-associated Hbp1 or Hbp2. Heme is then transferred to the ABC transporter HupDGC or Lmo2182–4 where it is used directly by the bacterium, or the porphyrin ring may be cleaved by an uncharacterized heme monooxygenase to release free iron for use by the bacterium.