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. Author manuscript; available in PMC: 2021 Oct 1.
Published in final edited form as: Trends Microbiol. 2020 May 4;28(10):821–831. doi: 10.1016/j.tim.2020.04.004

Figure 2: Heme sensing and signaling in S. aureus.

Figure 2:

(1) Heme is imported into the cytoplasm via the Isd system. It has been proposed that Hts, which has an established role in siderophore import, may also play a role in heme transport. (2) The HssS histidine kinase is activated by a heme-associated stimulus. Whether HssS directly senses heme or a byproduct of heme metabolism remains unknown. (3) Activation of HssS results in autophosphorylation of HssS and transphosphorylation of the HssR response regulator. Phosphorylated HssR binds to the promoter sequence of hrtAB and stimulates its transcription via recruitment of RNA polymerase. (4) Heme, or a heme-associated byproduct, is effluxed by the HrtAB exporter.