Fig. 2. HphA is a heme-binding protein dependent on HsmA for secretion.

a Western blots demonstrate that A. baumannii secretes HphA into the supernatant, and secretion is HsmA dependent. GroEL is used as a control for cell lysis. Western blots are representative of three independent experiments. C and S refer to cell pellet and supernatant, respectively. b Rotated side representations of the structure of holo HphA bound to a molecule of heme. c Detailed view of the heme-binding site. Residue side chains in close proximity to heme are depicted as sticks, and polar contacts in cyan.