Protein involved in the movement of sodium ions across energy- transducing cell membranes. Primary active sodium transport is coupled to an energy-yielding chemical reaction such as ATP hydrolysis. Secondary active transport utilizes the voltage and ion gradients produced by the primary transport to drive the cotransport of other ions or molecules. These may be transported in the same (symport) or opposite (antiport) direction.

Protein involved in the transport of a molecule (metabolite, protein, etc), a ion or an electron across cell membranes, inside the cell or in a tissue fluid.

Protein which is part of a transmembrane protein complex that forms a hydrophilic channel across the lipid bilayer through which specific inorganic ions can diffuse down their electrochemical gradients. The channels are usually gated and only open in response to a specific stimulus, such as a change in membrane potential (voltage-gated) or the binding of a ligand (ligand-gated channel).

Protein which is part of a cation channel permeable for sodium found in the plasma membrane and in intracellular membranes. Sodium channels have been classified according to their gating mechanisms, which may depend on changes in the transmembrane electric field (voltage-gated sodium channels) or not (non-voltage-gated sodium channels, e.g. degenerins which are permeable also to lithium and potassium). Voltage-gated sodium channels, by opening in response to membrane depolarization, allow sodium entry and thus the propagation of depolarization along the plasma membrane of nerve, muscle and other electrically excitable cells. They play a role in different processes such as sensation, emotions, thought and movement. Another class of sodium channel is the degenerin/epithelial sodium channel (ENaC) superfamily, which is a group of proteins involved in diverse biological processes, including sodium homeostasis, salt taste, nociception, pain transduction, touch sensation and mechanotransduction.

A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.