Full-length Gα(q)-phospholipase C-β3 structure reveals interfaces of the C-terminal coiled-coil domain.

Phospholipase C-β (PLCβ) is directly activated by Gαq, but the molecular basis for how its distal C-terminal domain (CTD) contributes to maximal activity is poorly understood. Herein we present both the crystal structure and cryo-EM three-dimensional reconstructions of human full-length PLCβ3 in complex with mouse Gαq. The distal CTD forms an extended monomeric helical bundle consisting of three antiparallel segments with structural similarity to membrane-binding bin-amphiphysin-Rvs (BAR) domains.

Molecular basis for activation of G protein-coupled receptor kinases.

G protein-coupled receptor (GPCR) kinases (GRKs) selectively recognize and are allosterically regulated by activated GPCRs, but the molecular basis for this interaction is not understood. Herein, we report crystal structures of GRK6 in which regions known to be critical for receptor phosphorylation have coalesced to stabilize the kinase domain in a closed state and to form a likely receptor docking site. The crux of this docking site is an extended N-terminal helix that bridges the large and small lobes of the kinase domain and lies adjacent to a basic surface of the protein proposed to bind anionic phospholipids.

Galpha q allosterically activates and relieves autoinhibition of p63RhoGEF.

Galpha(q) directly activates p63RhoGEF and closely related catalytic domains found in Trio and Kalirin, thereby linking G(q)-coupled receptors to the activation of RhoA. Although the crystal structure of G alpha(q) in complex with the catalytic domains of p63RhoGEF is available, the molecular mechanism of activation has not yet been defined. In this study, we show that membrane translocation does not appear to play a role in G alpha(q)-mediated activation of p63RhoGEF, as it does in some other RhoGEFs.

Structure and function of heterotrimeric G protein-regulated Rho guanine nucleotide exchange factors.

Activation of certain classes of G protein-coupled receptors (GPCRs) can lead to alterations in the actin cytoskeleton, gene transcription, cell transformation, and other processes that are known to be regulated by Rho family small-molecular-weight GTPases. Although these responses can occur indirectly via cross-talk from canonical heterotrimeric G protein cascades, it has recently been demonstrated that Dbl family Rho guanine nucleotide exchange factors (RhoGEFs) can serve as the direct downstream effectors of heterotrimeric G proteins. Heterotrimeric Galpha(12/13), Galpha(q), and Gbetagamma subunits are each now known to directly bind and regulate RhoGEFs.