Structure and Function Relationships of Heme-Based Gas Sensors and Heme-Redox Sensors

The heme-iron complex acts as the gas (O₂, NO and CO)-sensing site in a heme-based gas sensor. This function is distinct from those of well-known heme proteins in which the heme-iron complex is the functional active center (e.g., the O₂-carrying hemoglobin; the electron transfer mediator, cytochrome c; and the monooxygenase, cytochrome P450). The heme-based gas sensor, in contrast, is composed of an N-terminal heme-bound gas-sensing domain and a C-terminal functional domain. The association/dissociation of a gaseous molecule to/from the heme-iron complex of a gas sensor triggers the functional domain to regulate various physiologically important functions (e.g., guanylate cyclase activity, phosphodiesterase activity, histidine kinase activity, methyl-accepting chemotaxis, and transcription). There are also heme-redox sensors; they have the same domain arrangement as the heme-based gas sensors, and are regulated by the heme-iron redox state. Many of the molecular mechanisms underlying the intra- and inter-molecular signal transductions of gas and redox sensors have been elucidated. I summarize our existing knowledge of the heme-based gas (O₂, NO and CO) sensors and heme-redox sensors. I then delineate the structure/function relationships and common characteristics of the bacterial, archaeal and mammalian heme-based gas sensors and heme-redox sensors.

Acknowledgements: This work was in part supported by Supported in part by Grants-in-Aid from Shantou University Medical College and from the National Natural Science Foundation of China (NSFC) (No. 31170736)

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