PRO provides an ontological representation of protein-related entities by explicitly defining them and showing the relationships between them. Each PRO term represents a distinct class of entities (including specific modified forms, orthologous isoforms, and protein complexes) ranging from the taxon-neutral to the taxon-specific (e.g. the entity representing all protein products of the human SMAD2 gene is described in PR:Q15796; one particular human SMAD2 protein form, phosphorylated on the last two serines of a conserved C-terminal SSxS motif is defined by
PR:000025934). Current release:
71.0, March 31, 2025.