NOE and two-dimensional correlated H-NMR spectroscopy of cytochrome <em>c</em>′ from <em>Chromatium vinosum</em>.

tH two-dimensional (nuclear Overhauser effect spectroscopy (NOESY) and two-dimensional correlated spectroscopy (COSY) spectra of cytochrome c&#39; from Chromatium vinosum have been obtained. The protein is of medium size (Mr 28000), essentially high spin (S = 5/2) although some quantum mechanical spin admixing with S = 3/2 may be present. Under these circumstances NOESY cross peaks have been revealed between geminal protons (α-CH2 propionate and β-CH2 protons of the bound histidine) and between α-CH2 propionate protons and the heme methyl groups. COSY maps have confirmed the geminal nature of the proton pairs, even with a linewidth as large as 900 Hz; the J value is about 12 Hz. This assignment has rationalized on a sound basis the biochemical behavior of this protein with pH and has showed the utility of this kind of spectroscopy for the other cytochromes c&#39; structures and analogous systems. [ABSTRACT FROM AUTHOR]