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An intramolecular binding site for the myristoylated amino‐terminus of Gα i
Author(s) -
Preininger Anita M.,
Meier Scott M.,
Funk Michael A.,
Iverson Tina M.,
Hamm Heidi E.
Publication year - 2008
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.22.1_supplement.812.9
Subject(s) - myristoylation , amino acid , n terminus , chemistry , c terminus , biochemistry , binding site , g protein , peptide sequence , palmitoylation , biology , stereochemistry , receptor , cysteine , gene , membrane , enzyme
GPCRs act as guanine exchange factors for G‐proteins, catalyzing nucleotide release. The amino terminus of Gα i subunits is subject to reversible palmitoylation, as well as myristoylation, which is a permanent, co‐translational modification. Previous work has demonstrated that unmyristoylated Gα i proteins exhibit a disordered amino terminus in the absence of Gβγ, while myristoylated amino terminal residues are ordered even in the absence of Gβγ [Medkova, M. (2002) Biochemistry 41 , 9963–9972; Preininger, A.M. (2003) Biochemistry 42 , 7931–7941], suggesting an intramolecular binding site for the amino terminus of myristoylated Gα i subunits. In order to determine the location of this binding site, we utilized a combination of biophysical, biochemical and crystallographic methods. Using site‐directed‐mutagenesis combined with quenching studies, the extreme amino terminus undergoes activation‐dependent quenching by tryptophan residues within 15 Å of the extreme amino terminus, and this quenching occurs on the same timescale as that seen for nucleotide exchange. A crystal structure of a myristoylated Gα i protein demonstrates that myristoylation alters the conformation of Trp 258 (between the α‐3 helix and the β‐5 strand in the GTPase domain of Gα i proteins), and implicates this region as a participant in the intramolecular binding of the myristoylated amino terminus of Gα i proteins. This work was supported by the National Institutes of Health (Grant 2R01 EY06062‐22A2).