Protein for which there is at least one variant within the same species, that is not directly responsible for a disease. We make use of this keyword only in the context of multicellular organisms.

Protein which contains a stretch of amino acids present in multiple copies.

Protein which is posttranslationally modified by the attachment of either a single phosphate group, or of a complex molecule, such as 5'- phospho-DNA, through a phosphate group. Target amino acid is usually serine, threonine or tyrosine residues (mostly in eukaryotes), aspartic acid or histidine residues (mostly in prokaryotes).

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.