Purification and G protein subunit regulation of a phospholipase C-beta from Xenopus laevis oocytes.

The Journal of Biological Chemistry
T M FiltzT K Harden

Abstract

Xenopus oocytes exhibit both pertussis toxin-sensitive and -insensitive inositol lipid signaling responses to G protein-coupled receptor activation. The G protein subunits Galphai, Galphao, Galphaq, Galphas, and Gbetagamma all have been proposed to function as activators of phospholipase C in oocytes. Ma et al. (Ma, H.-W., Blitzer, R. D., Healy, E. C., Premont, R. T., Landau, E. M., and Iyengar, R. J. Biol. Chem. 268, 19915-19918) cloned a Xenopus phospholipase C (PLC-betaX) that exhibits homology to the PLC-beta class of isoenzymes. Although this enzyme was proposed to function as a signaling protein in the pertussis toxin-sensitive inositol lipid signaling pathway of oocytes, its regulation by G protein subunits has not been directly assessed. As such we have utilized baculovirus-promoted overexpression of PLC-betaX in Sf9 insect cells and have purified a recombinant 150-kDa isoenzyme. PLC-betaX catalyzes hydrolysis of phosphatidylinositol(4,5)bisphosphate and phosphatidylinositol(4)monophosphate, and reaction velocity is dependent on Ca2+. Recombinant PLC-betaX was activated by both Galphaq and Gbetagamma. PLC-betaX exhibited a higher apparent affinity for Galphaq than Gbetagamma, and Galphaq was more efficacious than Gbetag...Continue Reading

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Citations

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Jan 21, 2001·The Journal of Biological Chemistry·P S MischelL F Reichardt
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Oct 12, 1999·The American Journal of Physiology·E KobrinskyA R Marks
Oct 4, 2000·Physiological Reviews·M J Rebecchi, S N Pentyala
Feb 17, 1998·Biochemical and Biophysical Research Communications·M MatsumotoK Taniyama
Nov 23, 2006·Biochemical Pharmacology·Jennifer S McCullarTheresa M Filtz

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