Resonance Raman studies of gas sensing heme proteins

Heme sensor proteins are present in organisms ranging from bacteria to mammals, typically consisting of a catalytic domain and a heme-containing sensor domain, which can bind diatomic gas molecules such as O-2, CO, and NO. Such ligand binding event can induce active site conformational changes that are subsequently propagated to the functional domain, ultimately activating/deactivating a series of biological events, such as aerotaxis, gene expression, changes the metabolic pathway, and so forth. Such regulatory events are crucial for the cell to fulfill the physiological functions by regulating enzyme activity in response to the external stimuli. Resonance Raman (rR) spectroscopy is an effective method to investigate the sensing mechanism of these structurally different associated sensor proteins that exhibit diverse inherent physiological functions. This review summarizes the results of rR studies on a diverse collection of these heme sensor proteins, including FixL, Escherichia coli direct oxygen sensor (EcDOS), HemAT from Bacillus subtilis (HemAT-Bs), CooA, soluble guanylyl cyclase (sGC), heme nitric oxide and/or oxygen binding domain (H-NOX), and nitric oxide sensing proteins (NosP).