This entry contains UfSP1 and UfSP2, which are cysteine peptidases required for the processing and activation of Ubiquitin fold modifier 1 (Ufm1, ) and for its release from conjugated cellular proteins. UfSP1 and UfSP2 are 217 aa and 461 aa respectively [, ]. The peptidases belong to MEROPS peptidase family C78, clan CA. The UfSP2 family have an N-terminal extension with one or more zinc finger domains of the C2H2 type, which have been shown to be involved in protein:protein interaction. UfSP2 is present in most, if not all, multi-cellular organisms including plants, nematodes, flies, and mammals, whereas UfSP1 is not present in plants and nematodes [].
This entry represents Ufm1 (ubiquitin-fold modifier), which is a ubiquitin-like protein with structural similarities to ubiquitin [, ]. Ufm1 is one of a number of ubiquitin-like modifiers that conjugate to target proteins in cells through Uba5 (E1) and Ufc1 (E2). The Ufm1-system is conserved in metazoa and plants, suggesting it has a potential role in multicellular organisms []. Human Ufm1 is synthesized as a precursor consisting of 85 amino-acid residues. Prior to activation by Uba5, the extra amino acids at the C-terminal region of Ufm1 are removed to expose Gly, which is necessary for conjugation to target molecule(s). C-terminal processing of Ufm1 requires two specific cysteine peptidases (): UfSP1 and UfSP2; both peptidases are also able to release Ufm1 from Ufm1-conjugated cellular proteins. UfSP2 is present in most, if not all, of multi-cellular organisms including plant, nematode, fly, and mammal, whereas UfSP1 is not present in plants and nematodes [].
