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Subunit interactions of the Go protein
Author(s) -
van der Voorn Loesje,
Hengeveld Trudi M.,
Ploegh Hidde L.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81054-p
Subject(s) - gtp' , protein subunit , chemistry , heterotrimeric g protein , g alpha subunit , gi alpha subunit , biochemistry , biophysics , activator (genetics) , g protein , biology , receptor , enzyme , gene
The monoclonal antibody, MONO, recognizes an epitope on the G protein αo‐subunit [van der Voorn et al., submitted] and readily immunoprecipitates heterotrimeric Go proteins from solubilized, crude bovine brain membranes, as well as from a purified bovine brain G protein preparation. Upon incubation of the immunoprecipitates with GTPγS, all βγ‐subunits are released from the αo‐subunit. Thus, binding of MONO to the Go protein does not appear to interfere with release of bound GDP, binding of GTPγS or GTPγS‐induced subunit dissociation. However, we have been unable to induce a similar dissociaton of Go using its physiological activator, GTP. Surprisingly, we did not observe any dissociation of Go (bound to MONO) upon dilution in a range from 500 to 5 nM. Since an apparent X 4 of αo‐GDP for binding βγ of 340–390 nM has been reported (1989) J. Biol. Chem. 264, 20688–20696] our results would suggest that binding of MONO to the αo‐subunit induces an increased affinity of αo‐GDP for βγ. Alternatively, these results could be explained if, under the conditions used, the K 4 of αo‐GDP for βγ were at least two orders of magnitude lower than estimated previously.