1H NMR studies of paramagnetic ferricytochrome c-551 from Pseudomonas aeruginosa at high pH: The role of histidine 16 in the spin transition

Abstract Cytochrome c-551 from the mesophile Pseudomonas aeruginosa is an electronic transfer protein that contains 82 amino-acid residues and a c-type heme as the prosthetic group with low spin Fe(II) in the reduced form and low spin Fe(III) in the oxidized form of cytochrome c-551. We have studied the electronic properties of ferricytochrome c-551 from P. aeruginosa at high pH (9–11.4) by means of paramagnetic 1H NMR spectra and the T1 and T2 values of isotropically shifted proton resonances. We have also analyzed the temperature dependence of the hyperfine-shifts. Resonance assignment of some signals was based on 2D saturation transfer experiments, EXSY. These results indicate the existe…