I. Bertini et al., ISOLATION AND CHARACTERIZATION OF CYTOCHROME C(2) FROM RHODOPSEUDOMONAS-PALUSTRIS, Inorganica Chimica Acta, 269(1), 1998, pp. 125-134
Cytochrome c(2) from Rhodopseudomonas palustris has been isolated and
characterized by UV-Vis, electron paramagnetic resonance and NMR spect
roscopy. The latter, through natural abundance H-1-C-13 heteronuclear
multiple quantum coherence experiments and homonuclear 2D spectra, all
owed us to assign the signals of the heme substituents and of the iron
-bound histidine and methionine. An analysis of the C-13 chemical shif
t of the heme substituents has allowed us to localize the axes of the
magnetic susceptibility tensor. The latter are consistent with the ori
entation of the two axial ligands as found from our NOE data. The pH d
ependence of the shifts showed a pK(a) = 6.9 and the presence of a fur
ther pK(a) above 8.0. The present investigation shows how the appropri
ate use of NMR spectroscopy can provide a wealth of structural and ele
ctronic information even in the absence of any biochemical data. (C) 1
998 Elsevier Science S.A.