Proton magnetic resonance spectra of Rhodospirillum rubrum cytochrome c2.

Nuclear magnetic resonance spectra of ferro- and ferricytochrome C(2) from the facultative photoheterotroph, Rhodospirillum rubrum, obtained with a 220-MHz spectrometer, are presented. Assignments to protons of various important structural groups in contact with or near the prosthetic heme group are given. These include (a) in the ferro-form, methyl, cbeta and cgamma protons of the extraplanar ligand residue, methionine 91, and methyl protons of the residue leucine 32; and (b) corresponding protons in the ferri-form with the addition of methyl protons from the condensation of a heme vinyl group with cysteine 17, a single proton from the condensation involving cysteine 14, and protons from the ring methyls. These resonances are compared with those corresponding to the same groups in horse heart cytochrome c.