Protein involved in the transport of ions. Such proteins are usually transmembrane and mediate a movement of ions across cell membranes. Transport may be passive (facilitated diffusion; down the electrochemical gradient), or active (against the electrochemical gradient). Active transport requires energy which may come from light, oxidation reactions, ATP hydrolysis, or cotransport of other ions or molecules.

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.

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.