Structure determination of membrane protein by both cryo-electron tomography and single particle analysis

Structure and regulation of phospholipase Cβ and ε at the membrane

Phospholipase C (PLC) β and ε enzymes hydrolyze phosphatidylinositol (PI) lipids in response to direct interactions with heterotrimeric G protein subunits and small GTPases, which are activated downstream of G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). PI hydrolysis generates second messengers that increase the intracellular Ca²⁺ concentration and activate protein kinase C (PKC), thereby regulating numerous physiological processes. PLCβ and PLCε share a highly conserved core required for lipase activity, but use different strategies and structural elements to autoinhibit basal activity, bind membranes, and engage G protein activators. In this review, we discuss recent structural insights into these enzymes and the implications for how they engage membranes alone or in complex with their G protein regulators.

Reconstitution of Membrane Proteins into Nanodiscs for Single-Particle Electron Microscopy

The structure determination of integral membrane protein (IMP) in lipid environment is particularly challenging. Among emerging methods for exchanging detergent required for IMP purification by original compounds, the use of lipid nanodisc preserves a lipid environment. Compared with the classical method of proteoliposome formation, the nanodisc technology provides a better control of IMP molecules inserted in lipid membrane, therefore giving access to structural methodologies developed for soluble proteins. Here, we present the reconstitution of OprM membrane protein into nanodisc associated with a step of size-exclusion chromatography, an approach applicable to prepare IMPs for subsequent visualization by single-particle electron microscopy.