TY - JOUR
T1 - A membrane-delimited pathway of G-protein regulation of the guard-cell inward K+ channel
AU - Wu, Wei Hua
AU - Assmann, Sarah M.
PY - 1994/7/5
Y1 - 1994/7/5
N2 - 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'-[γ-thio]triphosphate, a nonhydrolyzable GTP analog that locks G proteins into their activated state, decreased the open state probability (P(o)) of single inward K+ channels. This decrease in P(o) was accompanied by an increase in one of the closed time constants of the K+ channel. Guanosine 5'-[β-thio]diphosphate, a GDP analog that locks G proteins into their inactivated state, slightly increased the P(o) 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 P(o) 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.
AB - 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'-[γ-thio]triphosphate, a nonhydrolyzable GTP analog that locks G proteins into their activated state, decreased the open state probability (P(o)) of single inward K+ channels. This decrease in P(o) was accompanied by an increase in one of the closed time constants of the K+ channel. Guanosine 5'-[β-thio]diphosphate, a GDP analog that locks G proteins into their inactivated state, slightly increased the P(o) 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 P(o) 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.
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U2 - 10.1073/pnas.91.14.6310
DO - 10.1073/pnas.91.14.6310
M3 - Article
C2 - 8022777
AN - SCOPUS:0028287237
SN - 0027-8424
VL - 91
SP - 6310
EP - 6314
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 14
ER -