1H NMR study of the reduced cytochrome c′ from Rhodopseudomonas palustris containing a high-spin iron(II) heme moiety

The assignment of the hyperfine shifted signals of the reduced cytochrome c' from Rhodopseudomonas palustris has been obtained through saturation transfer experiments with assigned signals of the high-spin oxidized protein and through tailored experiments to reveal proton-proton dipolar connectivities in paramagnetic molecules. The peculiar shift pattern consisting of the 1-, 8-, and 5-methyl signals shifted upfield and the 3-methyl signal downfield, which is shared by all cytochromes c' so far described, has been semiquantitatively related to the orientation of the histidine plane with respect to the iron-heme nitrogen axes. The research is meaningful with respect to the use of paramagnetic NMR as a tool to obtain direct structural information on all high spin iron(II) heme containing systems, including deoxyglobins.