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Two Distinct Sites on Gβγ are Required for Binding to the N‐Terminus Versus the Activation Site on Adenylyl Cyclase
Author(s) -
Brand Cameron S.,
Sadana Rachna,
Malik Sundeep,
Smrcka Alan V.,
Dessauer Carmen W.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1011.7
Subject(s) - heterotrimeric g protein , adenylyl cyclase , gs alpha subunit , g protein , microbiology and biotechnology , effector , binding site , biology , chemistry , stimulation , biochemistry , signal transduction , neuroscience
The heterotrimeric G protein α and βγ subunits are important regulators of adenylyl cyclase (AC), which controls synthesis of the second messenger cyclic AMP. In the inactive state, critical effector sites on Gα and Gβγ are not available. When activated, the subunits either dissociate or rearrange to expose these sites to effectors. However, we have previously shown that AC5 binds to inactive Gs heterotrimer at its N‐terminus (NT), while Gβγ conditional stimulation of AC5 is independent of this binding site. Both FRET and BiFC in live cells support interactions between Gβγ and AC5 that are at least partially dependent on the NT. We hypothesize that Gβγ utilizes two different surfaces to interact with the NT versus the activation sites on AC5 and AC6. In support of this hypothesis, mutations of the Gβγ effector surface were tested for Gβγ conditional stimulation of AC5 and for binding to AC5‐NT. Several Gβγ mutants, including W99A, are unable to support Gβγ activation, but have no effect on Gβγ binding to AC5‐NT. We have also utilized the SIGK peptide as a competition inhibitor of Gβγ “hotspot” interactions. SIGK is a strong inhibitor of Gβγ stimulation of AC6, but has little effect on Gβγ binding to AC6‐NT. Furthermore, Gβγ binds to the NT of many AC isoforms, suggesting that AC anchoring of heterotrimer may be a common theme for ACs to facilitate regulation by both α and βγ subunits. Supported by NIH grant GM60419 and AHA.