An essential step in many signaling cascades is inositol lipid hydrolysis catalyzed by phospholipase C–β. The latter is activated by the α subunit of the heterotrimeric G protein Gq, and it in turn inactivates Gαq, thus sharpening the signal. Waldo et al. report structural and biochemical data that explain the basis of this reciprocal regulation. One domain of phospholipase C–β binds to activated Gαq. Although the phospholipase C–β active site remains occluded in the structure, the plug is probably removed upon G protein–dependent orientation of the lipase at the membrane. A second domain of phospholipase C–β accelerates guanosine triphosphate hydrolysis by Gαq, causing the signaling complex to dissociate.
G. L. Waldo, T. K. Ricks, S. N. Hicks, M. L. Cheever, T. Kawano, K. Tsuboi, X. Wang, C. Montell, T. Kozasa, J. Sondek, T. K. Harden, Kinetic scaffolding mediated by a phospholipase C–β and Gq signaling complex. Science 330, 974–980 (2010). [Abstract] [Full Text]