Regulatory interaction of the Ga protein with phospholipase A2 in the plasma membrane of Eschscholzia californica 

 -  The Plant Journal, 52(6), p.1041-1051, 2007 .
<br/><br/> Plant heterotrimeric G-proteins are involved in a variety of signaling pathways, though only one a and a few bc isoforms of their subunits exist. In isolated plasma membranes of California poppy (Eschscholzia californica), the plant-specific Ga subunit was isolated and identified immunologically and by homology of the cloned gene with that of several plants. In the same membrane, phospholipase A2 (PLA2)was activated by yeast elicitor only if GTPcS (an activator of Ga)was present. From the cholate-solubilized membrane proteins, PLA2 was co-precipitated together with Ga by a polyclonal antiserum raised against the recombinant Ga. In this immunoprecipitate and in the plasma membrane (but not in the Ga-free supernatant)PLA2 was stimulated by GTPcS. Plasma membranes and immunoprecipitates obtained from antisense transformants with a low Ga content allowed no such stimulation. An antiserum raised against the C-terminus (which in animal Gas is located near the target coupling site)precipitated Ga without any PLA2 activity. Using non-denaturing PAGE, complexes of solubilized plasma membrane proteins were visualized that contained Ga plus PLA2 activity and dissociated at pH 9.5. At this pH, PLA2 was no longer stimulated by GTPcS. It is concluded that a distinct fraction of the plasma membrane-bound PLA2 exists in a detergent-resistant complex with Ga that can be dissociated at pH 9.5. This complex allows the Ga-mediated activation of PLA2. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>PLANT G(ALPHA)PROTEIN<br/>PHOSPHOLIPASE A2<br/>PLANT SIGNAL TRANSFER<br/>MEMBRANE PROTEIN COMPLEXES<br/>PLASMA MEMBRANE PROTEINS