Purification, G protein activation, and partial amino acid sequence of a novel phospholipase C from squid photoreceptors

Biochemistry
J Mitchell, L H Mayeenuddin

Abstract

Invertebrate visual signal transduction is initiated by rhodopsin activation of a guanine nucleotide binding protein, Gq, which stimulates phospholipase C (PLC) activity. We have previously purified a 140-kDa PLC enzyme from squid photoreceptors that is regulated by squid Gq. In these studies, an additional PLC enzyme was purified from the cytosol of squid photoreceptors and identified as a 70-kDa protein by SDS-polyacrylamide gel electrophoresis. Hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by PLC-70 was optimal at pH 5 in the presence of 100 microM Ca2+ with a specific activity of 10.3 micromol min-1 mg-1. A polyclonal antibody raised against purified PLC-70 did not recognize purified PLC-140, and proteolytic digestion of the two purified enzymes with trypsin or Staphylococcus aureaus V8 protease showed distinct patterns of peptide fragments, indicating that PLC-70 is not a fragment of PLC-140. The partial amino acid sequence of the protein showed homology with PLC21 and norpA isozymes cloned from Drosophila, and mammalian PLC beta isozymes. Reconstitution of purified GTPgammaS-bound soluble squid Gq with PLC-70 resulted in significant enhancement of PIP2 hydrolysis over a range of Ca2+ concentrations and shifte...Continue Reading

References

Jan 1, 1988·Journal of Biochemistry·H InoueY Hotta
Jan 1, 1982·Methods in Enzymology·D S Papermaster

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Citations

Aug 2, 2003·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·Lynle Go, Jane Mitchell
Apr 16, 2003·Journal of Neurochemistry·Linnia H Mayeenuddin, Jane Mitchell
Jan 18, 2007·The Journal of Comparative Neurology·Arie Sitthichai MobleyMary T Lucero
Jun 19, 2015·Pharmacological Reviews·Pertti PanulaHelmut L Haas
Apr 18, 2001·The Journal of Biological Chemistry·Z GombosM Ikura

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