The FIST C domain is a novel sensory domain, which is present in signal transduction proteins from Bacteria, Archaea and Eukarya. Chromosomal proximity of FIST-encoding genes to those coding for proteins involved in amino acid metabolism and transport suggest that FIST domains bind small ligands, such as amino acids [1].

1: FIST: a sensory domain for diverse signal transduction pathways in prokaryotes and ubiquitin signaling in eukaryotes. Borziak K, Zhulin IB; Bioinformatics. 2007;23:2518-2521. PMID:17855421