A membrane-delimited pathway of G protein regulation of the guard-cell inward K+channel
by Wu W. H., Assmann S. M. (1994)
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in Proc Natl Acad Sci USA 91: 6310–6314 – https://doi.org/10.1073/pnas.91.14.6310 –
Abstract
GTP-binding protein (G-protein) regulation of inward rectifying K+ channels in the plasma membrane of Vicia (Vicia faba L.) guard cells has previously been demonstrated at the whole-cell level. However, whether a cytosolic signal transduction chain is required for G-protein regulation of K+ channels in Vicia guard cells, or in any plant cell type, remains unknown.
In the present study, we assayed effects of several G-protein regulators on inward K+ channels in isolated inside-out membrane patches from Vicia guard cell protoplasts. Guanosine 5′-[gamma-thio]triphosphate, a nonhydrolyzable GTP analog that locks G proteins into their activated state, decreased the open state probability (Po) of single inward K+ channels. This decrease in Po was accompanied by an increase in one of the closed time constants of the K+ channel. Guanosine 5′-[beta-thio]diphosphate, a GDP analog that locks G proteins into their inactivated state, slightly increased the Po of the inward K+ channel and shortened the closed time constants.
Pertussis toxin and cholera toxin, which ADP-ribosylate G proteins at different sites, decreased the Po of the inward K+ channel.
Our data indicate that G proteins can act via a membrane-delimited pathway to regulate inward K+ channels in the guard-cell plasma membrane.
PLANT STOMATA ENCYCLOPEDIA 