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PDBsum entry 5kdo
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Signaling protein
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PDB id
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5kdo
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Contents |
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340 a.a.
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335 a.a.
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56 a.a.
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References listed in PDB file
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Key reference
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Title
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A conserved hydrophobic core in gαi1 regulates g protein activation and release from activated receptor.
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Authors
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A.I.Kaya,
A.D.Lokits,
J.A.Gilbert,
T.M.Iverson,
J.Meiler,
H.E.Hamm.
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Ref.
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J Biol Chem, 2016,
291,
19674-19686.
[DOI no: ]
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PubMed id
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Abstract
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G protein-coupled receptor-mediated heterotrimeric G protein activation is a
major mode of signal transduction in the cell. Previously, we and other groups
reported that the α5 helix of Gαi1, especially the hydrophobic interactions in
this region, plays a key role during nucleotide release and G protein
activation. To further investigate the effect of this hydrophobic core, we
disrupted it in Gαi1 by inserting 4 alanine amino acids into the α5 helix
between residues Gln(333) and Phe(334) (Ins4A). This extends the length of the
α5 helix without disturbing the β6-α5 loop interactions. This mutant has high
basal nucleotide exchange activity yet no receptor-mediated activation of
nucleotide exchange. By using structural approaches, we show that this mutant
loses critical hydrophobic interactions, leading to significant rearrangements
of side chain residues His(57), Phe(189), Phe(191), and Phe(336); it also
disturbs the rotation of the α5 helix and the π-π interaction between His(57)
and Phe(189) In addition, the insertion mutant abolishes G protein release from
the activated receptor after nucleotide binding. Our biochemical and
computational data indicate that the interactions between α5, α1, and β2-β3
are not only vital for GDP release during G protein activation, but they are
also necessary for proper GTP binding (or GDP rebinding). Thus, our studies
suggest that this hydrophobic interface is critical for accurate rearrangement
of the α5 helix for G protein release from the receptor after GTP binding.
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