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. Author manuscript; available in PMC: 2016 Aug 2.
Published in final edited form as: J Am Chem Soc. 2015 Jun 24;137(26):8435–8449. doi: 10.1021/jacs.5b01493

Table 1.

Reduction Potentials and Proposed Ligand Exchange Processes for Studied Variants of Yeast iso-1 Cyt c at pH 7.4a,b

Variant Em (mV vs SHE) Proposed Redox Reactions and Ligand
Exchange Processes
T78C/K79G solution 22 ± 7
(82 ± 3)c 		CysFe(III)→MetFe(III)↔MetFe(II)
(MetFe(II)↔MetFe(III)→CysFe(III))c
T78C/K79G/M80Ld −340 CysFe(III)↔CysFe(II)
K73A/K79G/M80K −94 ± 2 LysFe(III)↔LysFe(II)
K79G 266 ± 2 MetFe(III)↔MetFe(II)
WT* 247 ± 4 MetFe(III)↔MetFe(II)
M80A −80 ± 5 (OH−)Fe(III)↔Fe(II)
T78C/K79G-maleimide 63 ± 4
(51 ± 5)c 		LysFe(III)→MetFe(III)↔MetFe(II)
(MetFe(II)↔MetFe(III)→LysFe(III))c
T78C/K79G crystal drope 83; −160 CysFe(III)→MetFe(III)↔Met(FeII);
(OH−)Fe(III)↔Fe(II) and/or
LysFe(III)↔LysFe(II)
a

All variants contained two background mutations K72A and C102S, to prevent Lys72 coordination to the heme iron and formation of Cys102-linked dimers, respectively.

b

The observed potentials are strongly affected when there is coupling to a ligand exchange process.

c

Reductive (oxidative) direction.

d

From ref. 32.

e

A mixture of heme-ligated species, from direct electrochemistry measurements (Figure S11).