Abstract:
:The effect of ionic strength on the macroscopic and microscopic redox potentials and the heme environment of cytochrome c3 from Desulfovibrio vulgaris Miyazaki F have been investigated by NMR and electrochemical methods. The redox potentials of this tetraheme protein are found to be ionic strength-dependent. Especially, the microscopic redox potentials of hemes 2 and 3 at the fourth reduction step increase significantly with increasing ionic strength, which is in contraction to the theoretical expectation. The coordinated imidazole proton signals are unaffected by ionic strength. However, the methyl and propionate proton signals of hemes 1 and 4 showed significant ionic strength dependencies that are distinct from those for hemes 2 and 3. This heme classification is the same as that found in the ionic strength dependencies of the microscopic redox potentials at the fourth reduction step. Furthermore, the effect of ionic strength on the electrostatic potentials at the heme irons has been examined on the theoretical basis. The electrostatic potential at heme 4 changes up to 1 M ionic strength, which was not expected from the observations reported on cytochromes so far. These results are discussed in connection with the reported anomalous ionic strength dependency of the reduction rate of cytochrome c3.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Ohmura T,Nakamura H,Niki K,Cusanovich MA,Akutsu Hdoi
10.1016/S0006-3495(98)74067-6subject
Has Abstractpub_date
1998-09-01 00:00:00pages
1483-90issue
3eissn
0006-3495issn
1542-0086pii
S0006-3495(98)74067-6journal_volume
75pub_type
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