DFT analysis of axial and equatorial effects on heme-CO vibrational modes: applications to CooA and H-NOX heme sensor proteins.

ABSTRACT: Determinants of the Fe-CO and C-O stretching frequencies in (imidazole)heme-CO adducts have been investigated via density functional theory (DFT) analysis, in connection with puzzling characteristics of the heme sensor protein CooA and of the H-NOX (Heme-Nitric Oxide and/or OXygen binding) family of proteins, including soluble guanylate cyclase (sGC). The computations show that two mechanisms of Fe-histidine bond weakening have opposite effects on the nuFeC/nuCO pattern. Mechanical tension is expected to raise nuFeC with little change in nuCO whereas the weakening of H-bond donation from the imidazole ligand has the opposite effect. Data on CooA indicate imidazole H-bond weakening associated with heme displacement, as part of the activation mechanism. The computations also reveal that prot

SUBMITTER: Xu C 

PROVIDER: S-EPMC2754214 | biostudies-literature | 2008 Feb

REPOSITORIES: biostudies-literature