Purification of recombinant G proteins from Sf9 cells by hexahistidine tagging of associated subunits: Characterization of α12 and inhibition of adenylyl cyclase by αz

Tohru Kozasa, Alfred G. Gilman

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Abstract

A method is described for purification of G protein α and βγ subunits from Sf9 cells infected with recombinant baculoviruses. The subunit to be purified is coexpressed with an associated subunit bearing a hexahistidine tag. After adsorption of the oligomer to a Ni2+-containing column, the subunit to be purified is eluted specifically by promoting subunit dissociation with AlF- 4. The α subunits of G12, Gq, Gz, and Gi1 and the β1γ2 subunit complex were easily and efficiently purified by this method. Results were superior to established procedures in all cases. Purified α12 was characterized for the first time. The protein has a slow rate of guanine nucleotide exchange (kon,GTPγS = 0.01 min-1) and a very slow kcat for hydrolysis of GTP (0.1-0.2 min-1). GTPγS (guanosine 5′-3-O-(thio)triphosphate)·α12 does not influence the activity of several adenylyl cyclases or phospholipases. Activated αz inhibits the activity of type I and type V adenylyl cyclases. It is a somewhat more potent inhibitor of type V adenylyl cyclase than is activated αi1.

Original languageEnglish (US)
Pages (from-to)1734-1741
Number of pages8
JournalJournal of Biological Chemistry
Volume270
Issue number4
Publication statusPublished - Jan 27 1995

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ASJC Scopus subject areas

  • Biochemistry

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