INVESTIGATION OF OXIDATION STATE-DEPENDENT CONFORMATIONAL-CHANGES IN DESULFOVIBRIO-VULGARIS HILDENBOROUGH CYTOCHROME-C(553) BY 2-DIMENSIONAL H-1-NMR SPECTRA

Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) was u sed to assign the proton resonances of ferricytochrome c(553) from Des ulfovibrio vulgaris Hildenborough. The spin systems of 76 out of 79 am ino acids were identified by J-correlation spectroscopy (COSY and HOHA HA) in H2O and D2O and correlated by nuclear Overhauser effect spectro scopy (NOESY), The proton chemical shifts are compared in both oxidize d and reduced states of the protein at 23 degrees C and pH 5.9, Chemic al shift variations between reduced and oxidized states are due to the paramagnetic contribution. Medium and long-range nOe demonstrate the lack of major changes between the two redox states, NMR data provide e vidence that in this low oxidoreduction potential cytochrome, the oxid ized state is more rigid than the reduced state.