Figl, Antonio and Labarca, Cesar and Davidson, Norman and Lester, Henry A. and Cohen, Bruce N. (1996) Voltage-Jump Relaxation Kinetics for Wild-type and Chimeric β Subunits of Neuronal Nicotinic Receptors. Journal of General Physiology, 107 (3). pp. 369-379. ISSN 0022-1295. http://resolver.caltech.edu/CaltechAUTHORS:20120208-075012754
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We have studied the voltage-jump relaxation currents for a series of neuronal nicotinic acetylcholine receptors resulting from the coexpression of wild-type and chimeric β4/β2 subunits with α3 subunits in Xenopus oocytes. With acetylcholine as the agonist, the wild-type α3β4 receptors displayed five- to eightfold slower voltage-jump relaxations than did the wild-type α3β2 receptors. In both cases, the relaxations could best be described by two exponential components of approximately equal amplitudes over a wide range of [ACh]'s. Relaxation rate constants increased with [ACh] and saturated at 20- to 30-fold lower concentrations for the α3β2 receptor than for the α3β4 receptor, as observed previously for the peak steady state conductance. Furthermore, the chimeric β4/β2 subunits showed a transition in the concentration dependence of the rate constants in the region between residues 94 and 109, analogous to our previous observation with steady state conductances. However, our experiments with a series of β-subunit chimeras did not localize residues that govern the absolute value of the kinetic parameters. Hill coefficients for the relaxations also differed from those previously measured for steady state responses. The data reinforce previous conclusions that the region between residues 94 and 109 on the β subunit plays a role in binding agonist but also show that other regions of the receptor control gating kinetics subsequent to the binding step.
|Additional Information:||© 1996 Rockefeller University Press. Original version received 14 August 1995 and accepted version received 13 November 1995. We thank Yinong Zhang, Michael Quick, Mark Nowak, and Craig Doupnik for helpful suggestions, Purnima Deshpande for expert technical help, and Jeremy Gollub, Heather Davis, and Brad Henkle for oocyte preparation and maintenance. This work was supported by grants from the National Institutes of Health (NS-t 1756) and from the California Tobacco-Related Disease Research Program (1 RT-0365, 1RT-0286).|
|Official Citation:||Voltage-jump relaxation kinetics for wild-type and chimeric β subunits of neuronal nicotinic receptors. A Figl, C Labarca, N Davidson, H A Lester, and B N Cohen J Gen Physiol 1996 107:369-379. Published March 1, 1996, doi:10.1085/jgp.107.3.369|
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|Deposited By:||Ruth Sustaita|
|Deposited On:||08 Feb 2012 16:41|
|Last Modified:||26 Dec 2012 14:48|
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