Study of the influence of NH S hydrogen bonds on the reduction potential in Clostridium pasteurianum 2(4Fe‐4S) ferredoxin using deuterium exchange

The effect of deuterium substitution of exchangeable hydrogen atoms on the reduction potential of Clostridium pasteurianum 2(4Fe‐4S) ferredoxin has been studied. The studies were conducted to determine if NH ⃛S hydrogen bonds to the iron–sulfur cluster are dominant in the mechanism of influence of the protein on cluster reduction potential, as has been proposed [Carter, C. W. (1977) J. Biol. Chem. 252, 7802–7811]. Deuteration of the slowly exchangeable hydrogen atoms, however, yields essentially no shift in the reduction potential (−0.2 ± 0.8 mV), suggesting that NH ⃛S bonds are not important modifiers of cluster reduction potential in this protein.