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Phospholipase C beta 3 (PLCb3) in solutionPhospholipase C beta 3 (PLCb3) in solution
Structural highlights
FunctionPLCB3_HUMAN The production of the second messenger molecules diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) is mediated by activated phosphatidylinositol-specific phospholipase C enzymes. Publication Abstract from PubMedPhospholipase C-betas (PLCbetas) catalyze the hydrolysis of phosphatidylinositol 4, 5-bisphosphate [Formula: see text] into [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text]. [Formula: see text] regulates the activity of many membrane proteins, while IP3 and DAG lead to increased intracellular Ca(2+) levels and activate protein kinase C, respectively. PLCbetas are regulated by G protein-coupled receptors through direct interaction with [Formula: see text] and [Formula: see text] and are aqueous-soluble enzymes that must bind to the cell membrane to act on their lipid substrate. This study addresses the mechanism by which [Formula: see text] activates PLCbeta3. We show that PLCbeta3 functions as a slow Michaelis-Menten enzyme ( [Formula: see text] ) on membrane surfaces. We used membrane partitioning experiments to study the solution-membrane localization equilibrium of PLCbeta3. Its partition coefficient is such that only a small quantity of PLCbeta3 exists in the membrane in the absence of [Formula: see text] . When [Formula: see text] is present, equilibrium binding on the membrane surface increases PLCbeta3 in the membrane, increasing [Formula: see text] in proportion. Atomic structures on membrane vesicle surfaces show that two [Formula: see text] anchor PLCbeta3 with its catalytic site oriented toward the membrane surface. Taken together, the enzyme kinetic, membrane partitioning, and structural data show that [Formula: see text] activates PLCbeta by increasing its concentration on the membrane surface and orienting its catalytic core to engage [Formula: see text] . This principle of activation explains rapid stimulated catalysis with low background activity, which is essential to the biological processes mediated by [Formula: see text], IP3, and DAG. Gbetagamma activates PIP2 hydrolysis by recruiting and orienting PLCbeta on the membrane surface.,Falzone ME, MacKinnon R Proc Natl Acad Sci U S A. 2023 May 16;120(20):e2301121120. doi: , 10.1073/pnas.2301121120. Epub 2023 May 12. PMID:37172014[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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