Regulation of purified subtypes of phosphatidylinositol-specific phospholipase C β by G protein α and βγ subunits

Alan V. Smrcka, Paul C. Sternweis

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384 Scopus citations


Specific antisera were produced to peptides representing the carboxyl termini of three subtypes of phosphatidylinositol-specific phospholipase C (PIPLC) β which have been identified by isolation of cDNAs (Kriz, R., Lin, L., Sultzman, L., Ellis, C., Heldin, C., Pawson, T., and Knopf, J. (1990) Ciba Found. Symp. 150, 112-127). Screening with the antisera indicates that PIPLC β3 is present in a variety of cell lines and rat tissues, whereas the distribution of PIPLC β1 and β2 is more restricted. A combination of conventional and immunoaffinity chromatographic techniques was used to purify PIPLC β1 and β3 from rat brain membranes. PIPLC β2 was purified from cytosol of HL60 cells. All three subtypes were activated by purified G protein α(q/11) subunits with the following relative efficacies: PIPLC β3 ≥ PIPLC β1 >> PIPLC β2. All three PIPLC subtypes were also activated by G protein βγ subunits with varying efficacies. The presence of βγ subunits depressed the ability of α(q/11) to activate PIPLC β1 and β3 at low Mg2+ concentrations (1 mM). At higher concentrations of Mg2+ (2 mM or greater), activation of PIPLC β3, but not PIPLC β1, by βγ and α(q/11) became additive. PIPLC β3 was activated by α(q/11) even in the presence of a saturating concentration of βγ subunits. This indicates that there are separate sites for interaction of PIPLCs with G protein subunits and that this interaction differs depending on the enzyme subtype and the concentration of Mg2+.

Original languageEnglish (US)
Pages (from-to)9667-9674
Number of pages8
JournalJournal of Biological Chemistry
Issue number13
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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