Cytochrome c possesses a positively charged surface which binds specif
ically to mitochondria enzymes and metabolites. The affinity of the cy
tochrome c surface to charged ligands is demonstrated by specific bind
ing to berate ions. The effect of the ionic bond formed between the be
rate and the cytochrome is observed in both H-1 and B-11 NMR spectra.
New narrow peaks with prolonged T-1 values appear in the B-11 spectrum
and are assigned to the bound tetrahedral berate ion. In the H-1 spec
trum changes are observed in the peaks of the iron ligand histidine 18
beta 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 berate-bound forms of the protein is established by a two-dimensio
nal exchange spectroscopy experiment. The k(diss) for the process is 2
4 +/- 2 s(-1), as measured at 5 degrees C by an inversion transfer exp
eriment. K-D values were calculated at several temperatures and range
from 67 +/- 7 mM at 2.7 degrees C to 143 +/- 14 mM at 14 degrees C. (C
) 1998 Elsevier Science S.A. All rights reserved.