1H NMR studies of paramagnetic ferricytochrome c-551 from Pseudomonas aeruginosa at high pH: The role of histidine 16 in the spin transition

The electronic structure of ferricytochrome c-551 from Pseudomonas aeruginosa at high pH has been investigated using paramagnetic NMR techniques. The results indicate the existence of a spin transition associated to the deprotonation of histidine-16 axially bound to iron(III), which would trigger the decoordination of the second axial ligand, methionine-61.