Hydrogen bonding interaction on the heme-bound ligand in the heme-based O2 sensor protein

HemAT is a signal transducer protein responsible for aerotaxis control of some bacteria and archaea, which contains a heme-containing globin domain as the sensor of its physiological effector, O-2. The interaction between the heme-bound ligand and the surrounding amino acid residue(s) plays a crucial role for selective sensing of O-2 and signal transduction by HemAT. In this work, we have elucidated by resonance Raman spectroscopy how O-2 and CO interact with HemAT-Hs and HemAT-Rr, HemAT from Halobacterium salinarum and Rhodospirillum rubrum, respectively. HemAT-Hs and HemAT-Rr showed three conformers in the O-2-bound form, as is the case of HemAT-Bs, HemAT from Bacillus subtilis. Though the hydrogen bonding patterns observed in the three conformers were the same for HemAT-Bs, HemAT-Hs, and HemAT-Rr, the involved residues for the hydrogen bonding interaction were different from one another. Copyright (C) 2008 Society of Porphyrins & Phthalocyanines.