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GTPase Acceleration as the Rate-Limiting Step in Arabidopsis G Protein-Coupled Sugar Signaling

Christopher A. Johnston, J. Philip Taylor, Yajun Gao, Adam J. Kimple, Jeffrey C. Grigston, Jin-Gui Chen, David P. Siderovski, Alan M. Jones and Francis S. Willard
Proceedings of the National Academy of Sciences of the United States of America
Vol. 104, No. 44 (Oct. 30, 2007), pp. 17317-17322
Stable URL: http://www.jstor.org/stable/25450233
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
GTPase Acceleration as the Rate-Limiting Step in Arabidopsis G Protein-Coupled Sugar Signaling
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Abstract

Heterotrimeric G protein signaling is important for cell-proliferative and glucose-sensing signal transduction pathways in the model plant organism Arabidopsis thaliana. AtRGS1 is a seven-transmembrane, RGS domain-containing protein that is a putative membrane receptor for D-glucose. Here we show, by using FRET, that D-glucose alters the interaction between the AtGPA1 and AtRGS1 in vivo. AtGPA1 is a unique heterotrimeric G protein a subunit that is constitutively GTP-bound given its high spontaneous nucleotide exchange coupled with slow GTP hydrolysis. Analysis of a point mutation in AtRGS1 that abrogates GTPase-accelerating activity demonstrates that the regulation of AtGPA1 GTP hydrolysis mediates sugar signal transduction during Arabidopsis development, in contrast to animals where nucleotide exchange is the limiting step in the heterotrimeric G protein nucleotide cycle.

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