2Research Program of Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland; E-mail: Liliya.Euro@helsinki.fi
* To whom correspondence should be addressed.
Received August 16, 2010; Revision received October 8, 2010
The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) is a component of the respiratory chain of various bacteria that generates a redox-driven transmembrane electrochemical Na+ potential. The Na+-NQR activity is known to be specifically inhibited by low concentrations of silver ions. Replacement of the conserved Cys377 residue with alanine in the NqrF subunit of Na+-NQR from Vibrio harveyi resulted in resistance of the enzyme to Ag+ and to other heavy metal ions. Analysis of the catalytic activity also showed that the rate of electron input into the mutant Na+-NQR decreased by about 14-fold in comparison to the wild type enzyme, whereas all other properties of NqrFC377A Na+-NQR including its stability remained unaffected.
KEY WORDS: Na+-translocating NADH:quinone oxidoreductase, NqrF, ferredoxin:NADP+ oxidoreductase, sensitivity to heavy metals, protein stability