ESCRT components help sort membrane cargo and remodel membranes, including formation of internal vesicles in an endosome. Ubiquitin can be a cargo-selection signal, but recognition and the membrane-remodelling steps are distinct operations.

The LacY transporter importing lactose in Escherichia coli. Binding of dephosphorylated EIIA glucose can inhibit transport and reduce inducer accumulation.

A bacterial sugar-uptake system coupling transport to phosphorylation using a phosphoenolpyruvate-derived phosphoryl relay. Its phosphorylation state also contributes to carbon-source regulation.

A sodium-coupled glucose transporter important in apical intestinal uptake. The sodium gradient maintained by basolateral pumping powers uptake against a glucose gradient.

A substance facilitating proton transfer across a membrane and dissipating the proton electrochemical gradient. It can uncouple respiration from ATP synthesis without directly inhibiting every electron-transfer reaction.

An ATP-regulated anion channel whose phosphorylation-dependent activity contributes to epithelial chloride transport. Its activation downstream of cyclic AMP is important in cholera-associated secretion.

An ion-powered rotary machine driving bacterial flagellar motion. Its energy source and conformational switch are separable: inward ion flux can power either rotational direction.

Movement of proteins and lipids between cellular compartments by vesicles, tubules, membrane fusion and selective retrieval.

hydrophobic mismatch is an energetic incompatibility between a membrane protein's hydrophobic span and the hydrophobic thickness of its surrounding lipid bilayer. Local deformation, altered conformation or changed association can partly accommodate it.

An integrin is a transmembrane adhesion receptor linking extracellular ligands to intracellular signalling and cytoskeleton interactions. Integrin-dependent contacts transmit force in many forms of cell migration; their necessity depends on the physical environment.

A cargo receptor links a transported component to sorting machinery. An ER export receptor can bind a soluble lumenal cargo while exposing a cytoplasmic recognition site to the coat.

A cell-surface protein whose phosphorylated intracellular region can recruit signalling adaptors.

In kidney podocytes, it is a component of the specialized filtration-slit architecture. Its intracellular signalling interactions can recruit Nck and actin-regulatory partners, connecting a membrane contact to cytoskeletal organization. ^[ref]

An experimental environment designed to shield hydrophobic protein surfaces while retaining relevant membrane properties. Detergent micelles, bicelles and lipid bilayer nanodiscs have different limitations.

A bacterial outer-membrane protein studied by NMR in optimized lipid nanodiscs.^[ref]

A receptor supporting uptake of transferrin-bound iron. RNA regulation involving its 3′ region can increase transcript stability during iron shortage.

An iron-export protein. IRE-containing transcripts can be regulated at biological translation, while protein-level and systemic regulation provide additional controls.

A SNARE protein contributes a helical segment to a membrane-fusion assembly. Complementary SNARE proteins on opposing membranes form a SNARE complex whose assembly helps pull the membranes together. Syntaxins, SNAP-25 and synaptobrevin illustrate different components of the neuronal machinery. Purified components reconstituted into separate liposomes can promote fusion, showing that these proteins participate directly in membrane rearrangement. Cellular control additionally involves targeting and regulatory factors. ^[ref]

Membrane fusion intermediate in which contacting membrane leaflets have merged while the aqueous compartments remain separate. A lipid mixing assay therefore need not establish full membrane fusion.

A readout of lipid redistribution between membrane biological populations, for example through fluorescence dequenching. It must be distinguished from aqueous content mixing and leakage.

A measurement of exchange between previously separate enclosed aqueous compartments. Leakage into the surrounding medium is a different event and needs a separate control.