Cytochrome c possesses a positively charged surface which binds specifically to mitochondria enzymes and metabolites. The affinity of the cytochrome c surface to charged ligands is demonstrated by specific binding to borate ions. The effect of the ionic bond formed between the borate and the cytochrome is observed in both 1H and 11B NMR spectra. New narrow peaks with prolonged T1 values appear in the 11B spectrum and are assigned to the bound tetrahedral borate ion. In the 1H spectrum changes are observed in the peaks of the iron ligand histidine 18β and the heme methyls 3 and 8. These changes are affected by the ionic strength of the solution. The exchange process between the free and borate-bound forms of the protein is established by a two-dimensional exchange spectroscopy experiment. The kdiss for the process is 24 ± 2 s 1, as measured at 5°C by an inversion transfer experiment. KD values were calculated at several temperatures and range from 67 ± 7 mM at 2.7°C to 143 ± 14 mM at 14°C.
|Number of pages||5|
|Journal||Inorganica Chimica Acta|
|State||Published - 15 May 1998|
- B NMR
- Borate ion
- Cytochrome c
- H NMR