Hyperfine correlation spectroscopy and electron spin echo envelope modulation spectroscopy study of the two coexisting forms of the hemeprotein cytochrome c6 from Anabaena Pcc7119.
Oxidized cytochrome c(6) from Anabaena PCC 7119 was studied by electron spin echo envelope modulation spectroscopy. Hyperfine couplings of the unpaired electron with several nuclei were detected, in particular those of the nitrogens bound to the iron atom. Combining the experimental information here presented and previous continuous wave-electron paramagnetic resonance and electron nuclear double resonance results, some details on the electronic structure of the heme center in the protein are obtained. These results are discussed on the basis of a molecular model that considers one unpaired electron localized mainly in the iron d orbitals and propagation of the spin density within the heme center via spin polarization of the nitrogen sigma-orbitals. The coexistence of two heme forms at physiological pH values in this c-type cytochrome is also discussed taking into account the experimental evidence.
Instituto de Ciencia de Materiales de Aragón, Consejo Superior de Investigaciones Cientificas-Universidad de Zaragoza, Zaragoza, Spain.
Inés
I
García-Rubio
Pablo J
PJ
Alonso
Milagros
M
Medina
Jesús I
JI
Martínez
D000465:Algorithms; D017033:Anabaena; D001426:Bacterial Proteins / Q000737:chemistry; D045365:Cytochromes c6 / Q000737:chemistry*; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004583:Electrons; D006418:Heme / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D017672:Nitrogen Compounds / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods
D001426:Bacterial Proteins; D045365:Cytochromes c6; D058085:Iron Compounds; D017672:Nitrogen Compounds; D006418:Heme