The NH 2 ‐terminal α subunit attenuator domain confers regulation of G protein activation by βγ complexes
Author(s) -
Dhanasekaran N.,
Osawa Shoji,
Johnson Gary L.
Publication year - 1991
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240470409
Subject(s) - g alpha subunit , adenylyl cyclase , gi alpha subunit , gamma subunit , heterotrimeric g protein , interleukin 10 receptor, alpha subunit , transducin , protein subunit , g protein , gs alpha subunit , interleukin 5 receptor alpha subunit , scn3a , biology , alpha (finance) , gtp' , microbiology and biotechnology , beta (programming language) , g beta gamma complex , gtp binding protein regulators , biochemistry , receptor , enzyme , gene , medicine , construct validity , nursing , patient satisfaction , computer science , programming language
Abstract G s and G i , respectively, activate and inhibit the enzyme adenylyl cyclase. Regulation of adenylyl cyclase by the heterotrimeric G s and G i proteins requires the dissociation of GDP and binding of GTP to the α s or α i subunit. The βγ subunit complex of G s and G i functions, in part, to inhibit GDP dissociation and α subunit activation by GTP. Multiple β and γ polypeptides are expressed in different cell types, but the functional significance for this heterogeneity is unclear. The βγ complex from retinal rod outer segments (βγ t ) has been shown to discriminate between α i and α s subunits (Helman et al: Eur J Biochem 169:431–439, 1987). βγ t efficiently interacts with α i ‐like G protein subunits, but poorly recognizes the α s subunit. βγ t was, therefore, used to define regions of the α i subunit polypeptide that conferred selective regulation compared to the α s polypeptide. A series of α subunit chimeras having NH 2 ‐terminal α i and COOH‐terminal α s sequences were characterized for their regulation by βγ t , measured by the kinetics of GTPγS activation of adenylyl cyclase. A 122 amino acid NH 2 ‐terminal region of the α i polypeptide encoded within an α i /α s chimera was sufficient for βγ t to discriminate the chimera from α s . A shorter 54 amino acid α i sequence substituted for the corresponding NH 2 ‐terminal region of α s was insufficient to support the α i ‐like interaction with βγ t . The findings are consistent with our previous observation (Osawa et al: Cell 63:697–706, 1990) that a region in the NH 2 ‐terminal moiety functions as an attenuator domain controlling GDP dissociation and GTP activation of the α subunit polypeptide and that the attenuator domain is involved in functional recognition and regulation by βγ complexes.