PLC beta 3 Gq

Unique bidirectional interactions of Phospholipase C beta 3 with G alpha QUnique bidirectional interactions of Phospholipase C beta 3 with G alpha Q

Introduction Phospholipase C (PLC) catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate [IP2] to the second messengers inositol 1,4,5-trisphosphate [IP3] and diacylglycerol [DAG] in an essential step for many physiological cascades. When the receptor is stimulated by ligand of some kind it increase exchange of guanosine diphosphate (GDP) for guanosine triphosphate (GTP) on Gαq. GTP-bound Gαq activates PLC- β3, and PLC- β3 increases up to three orders of magnitude the rate of hydrolysis of GTP by its activating G protein. This is a unique mechanism when the PLC-β3 enzyme has the ability to terminate the Gαq protein signal in addition to being activated by it. Structural highlights The Gαq subunit consists two domains, one is the GTPase domain and the other is the alpha helical domain. These domains include three regions called . consisting of N-terminal PH domain, a series of four EF hands, a catalytic TIM barrel that the X/Y linker connect its two halves and a C2 domain. PLC- β3 engages Gαq throughout three regions. First, an extended loop between the third and fourth EF hands of PLC- β3 directly supports switch residues critical for GTP hydrolysis by Gαq. Second, the region of PLC- β3 that connects the catalytic TIM barrel and the C2 domain interacts with both switches 1 and 2 of Gαq. Third, a segment composed of a helix-turn-helix at the C terminus of the C2 domain mostly located within a shallow declivity on the surface of Gαq formed by switch 2 and α3. PLC-β3 interacts with a surface on Gαq that with portions of Gα subunits needed for engagement of RGS proteins and the effector-binding region. Other effectors are known to engage the within Gα subunits. There are a large family of regulator of G protein signaling (RGS) proteins that independently accelerates the GTP hydrolysis in the .

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