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Figure 5. . Nonstationary noise analysis of the interacting MTSET-IKCa mutants. Relationship between the current variance σ2 and the mean current during MTSET application illustrated for the V275C, A283C, V284C, and V285C mutants. and σ2 were measured on successive time periods of 1 s for A283C, V284C, and V285C and 0.5 s for V275C. The V275C mutant displayed a constant σ2/ (left panel right scale) ratio despite an important decrease in (left panel left scale), indicating an important inhibition of the channel unitary current. This proposal is also supported by the fact that the ratio σ2/2 (right panel) increases in this case with a time constant equal to τi, the inhibition time constant measured for . A similar noise pattern was also observed with the V284C mutant, although in this case the variations in σ2/ and σ2/2 can be accounted for a partial inhibition of the channel unitary current plus a decrease in channel open probability. A different noise behavior is, however, observed with the A283C and V285C channels. The decrease in σ2/2 observed with A283 correlates the increase in mean current with the σ2/ ratio remaining constant for time >7.5 s. This noise pattern would be compatible with a system where PB > PO with PO and PB << 1, thus supporting a model whereby the action of MTSET consists either to increase the channel open probability or recruit silent A283C mutants. The results obtained with V285C follow a similar pattern, although in this case the fact that the measured variation in σ2/2 is more important than the mean current increase favors a system where PB > PO with PO << 1. Image published in: Simoes M et al. (2002) Copyright © 2002, The Rockefeller University Press. Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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