Activity measurements of nineteen mutants of the L, M, and N subunits.

aActivity was measured in membrane preparations as described in “Materials and Methods”.bActivity is expressed as a percentage of the wild type value.cAn upper limit is estimated for the IC50 values based on two sets of inhibition data.dThe means, standard deviations and (number of measurements) are shown. For ferricyanide reductase, 2–3 measurements were made.eND, not determined.