Shaker家族门控特性.ppt

Presented by SONG Xindong 03/04/09 Outlines Intro to Shaker channel Experimental Results Hypothesized Schemes Models Intro to Shaker channels First cloned K+ channel gene By Jan, L Jan, Y N in 1987 Encoded one subunit Tetramer # not determined by the time of this paper A null mutant Sh KS133 Fly’s propensity to shake under ether anesthesia Outlines Intro to Shaker channel Experimental Results Hypothesized Schemes Models Phenomena of MACROSCOPIC recording Phenomena of MACROSCOPIC recording Phenomena of SINGLE CHANNEL recording Phenomena of SINGLE CHANNEL recording Parameters measured here burst # per voltage pulse open duration time # of openings per burst closed duration within bursts first latency probability of blank record Parameters INDEPENDENT with voltage burst # per voltage pulse open duration time opening # per burst burst closed duration Parameters INDEPENDENT with voltage burst # per voltage pulse Parameters INDEPENDENT with voltage open duration time Proposed Scheme 1 2 Parameters INDEPENDENT with voltage openings # per burst Parameters INDEPENDENT with voltage burst closed duration Events after first openings are V independent Parameters DEPENDENT on voltage first latency probability of blank record Parameters DEPENDENT on voltage first latency Parameters DEPENDENT on voltage Probability of blank record Scheme by now we get Outlines Intro to Shaker channel Experimental Results Hypothesized Schemes Models Assumptions before Schemes Gating can be described by a time-homogeneous Markov process The channel reaches equilibrium among the states in the model during the 500-ms prepulses used to measure the voltage dependence of resting inactivation Activation comes about by the independent movement of identical charges Closed state inactivation rates are not voltage dependent Closings during bursts are to preopen(resting) closed states Rate constants depend exponentially on membrane potential Fit the voltage dependent rates Other co