Examining the Proton Channels in Heme -Copper Oxidases
Previous work on the mutant enzyme KI-362M indicated that a block in the K-channel would result in the blockage of the catalytic cycle between the oxidized state and the two electron reduced state. This blockage occurs because an electron cannot enter the binuclear center without a proton to maintain the charge balance. If electrons cannot enter the binuclear center then the rate of reduction of the binuclear center is impaired. The E II-101 mutant enzymes had apparent first order rate constants, for the reduction of the binuclear center, between 0.56 and 15 s-1 compared to 159 s-1 for the wild-type enzyme. The measured rates of formation of other catalytic cycle intermediates were identical to wild-type. The data support the conclusion that EII-101 is the entrance to K-channel.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign