Ufm1 shares several common properties with ubiquitin (Ub) and other ubiquitin-like molecules (UBLs). Ufm1 has similar tertiary structure to Ub but lacks any obvious sequence similarity. It is synthesized as an inactive precursor form (pro-Ufm1) which has 2 additional amino acids beyond the conserved glycine. The mechanism of Ufm1 conjugation is similar to that of ubiquitin. Mature Ufm1 has an exposed C-terminal glycine which is essential for subsequent activation by its cognate E1 protein (Uba5). This activation step results in the formation of a high-energy thiolester bond in the presence of ATP. The Ufm1 is subsequently transferred to its cognate E2-like enzyme (Ufc1) via a similar thioester linkage with a cysteine at the E2 active site. Ufm1 is conjugated to a variety of target proteins and forms complexes with as yet unidentified proteins.