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Title
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Binding of G protein beta gamma-subunits to pleckstrin homology domains.
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Authors
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K.Touhara,
J.Inglese,
J.A.Pitcher,
G.Shaw,
R.J.Lefkowitz.
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Ref.
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J Biol Chem, 1994,
269,
10217-10220.
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PubMed id
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Abstract
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Ligand-induced activation of many receptors leads to dissociation of the alpha-
and beta gamma-subunit complexes of heterotrimeric G proteins, both of which
regulate a variety of effector molecules involved in cellular signaling
processes. In one case, a cytosolic enzyme, the beta-adrenergic receptor kinase
(beta ARK) binds to the dissociated, prenylated, membrane-anchored beta
gamma-subunits of heterotrimeric G proteins (G beta gamma) and is thereby
targeted to its membrane-bound receptor substrate. Quite recently, numerous
proteins involved in cellular signal transduction have been shown to contain
sequences homologous with a "domain" originally identified in the protein
"pleckstrin" (pleckstrin homology domain; PH domain) and subsequently found in
the G beta gamma interaction region of the beta ARK sequence. Here we
demonstrate that glutathione S-transferase-fusion proteins, containing sequences
encompassing the PH domain of nine proteins from this group, bind G beta gamma
to varying extents. Binding of G beta gamma to these fusion proteins was
documented either by a direct binding assay or by ability to block G beta
gamma-mediated membrane translocation of beta ARK1. G beta gamma binding to
these fusion proteins was inhibited by the alpha subunit of Go (Go alpha),
indicating that the binding of G beta gamma to G alpha and the PH
domain-containing fusion proteins is mutually exclusive. Studies with a series
of truncated PH domains derived from the Ras-guanine-nucleotide-releasing factor
indicate that the G beta gamma binding domain includes only the C-terminal
portion of the PH domain and sequences just distal to this. Protein-protein
interactions between G beta gamma and PH domain-containing proteins may play a
significant role in cellular signaling analogous to that previously demonstrated
for Src homology 2 and 3 domains.
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