Anti-FKBP prolyl isomerase 4 antibodies are used for the immunodetection of the protein encoded by the FKBP4 gene. In humans, the canonical protein has a reported length of 459 amino acid residues and a mass of 51.8 kDa. Its subcellular localization is in the nucleus, mitochondria, and cytoplasm. It is widely expressed across many tissue types. It is noted to be involved in the transport of ions and protein folding. Post-translational modifications have been described, including phosphorylation. Other names for this target antigen include FKBP52, FKBP59, HBI, Hsp56, PPIase, p52, peptidyl-prolyl cis-trans isomerase FKBP4, and FKBP51. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.