Two α subunits of the Gq class of G proteins stimulate phosphoinositide phospholipase C‐β1 activity

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Abstract
Two G protein α subunits were detected in preparations of GTPγS‐dependent, phosphoinositide‐specific phospholipase C‐activating proteins from bovine liver membranes. Partial resolution of the two α subunits, of molecular mass 42 and 43 kDa, was achieved by Mono Q chromatography. Quantitation of the levels of each α subunit and reconstitution assays demonstrated that each possessed stimulatory activity towards the β1 isozyme of phospholipase C. Immunoblot analysis showed that the 42 kDa protein was immunologically related to αq, whereas the 43 kDa protein was related to α11, another member of the Gq class. The data thus show that two different α subunits of the Gq class of G proteins stimulate phospholipase C‐β1 Activity.