13C and proton NMR studies of horse cytochrome c. Assignment and temperature dependence of methyl resonances.

The 13C and proton chemical shifts of the 55 methyl groups of horse cytochrome c have been determined over a range of temperatures both in the diamagnetic ferrocytochrome and in the paramagnetic ferricytochrome. Specific assignments of many proton resonances have been published previously and all of the remaining methyl proton resonances are now specifically assigned. The corresponding 13C assignments follow directly, including those of contact shifted 13C resonances which are reported for the first time.