Research ArticleBiochemistry

Nucleotide exchange–dependent and nucleotide exchange–independent functions of plant heterotrimeric GTP-binding proteins

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Science Signaling  05 Nov 2019:
Vol. 12, Issue 606, eaav9526
DOI: 10.1126/scisignal.aav9526

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Plant G proteins gain independence

Heterotrimeric guanine nucleotide–binding proteins (G proteins) are composed of α, β, and γ subunits. In animals, inactive G proteins contain GDP-bound Gα. Upon GDP-GTP exchange, the Gα becomes activated, dissociates from the βγ dimer, and stimulates effectors. The intrinsic GTPase activity of Gα returns the G protein to the resting state. Maruta et al. expressed wild-type Gα, a GTPase-deficient Gα mutant, or a Gα mutant unable to bind to guanine nucleotides in Arabidopsis plants deficient in the canonical Gα subunit AtGPA1. Some of the phenotypes caused by AtGPA1 loss, such as smaller flowers and rounder leaves, were rescued by the expression of either Gα mutant, suggesting that plant G proteins can function independently of guanine nucleotide exchange.

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