ARD1 is a member of the 2-kDa ARF protein family. It is a multifunctional protein. ARD1 has an 18-kDa ADP-ribosylation factor (ARF) domain at the C-terminus (amino acids 43-574), and a 46-kDa N-terminal domain (amino acids 1-42). The C-terminal region of ARD1 may be involved in the formation of both ARD1-ARD1 and ARD1-NAT1 complexes. ARD1 and NAT1 genes are required for the expression of an N-terminal protein acetyltransferase. This activity is required for full repression of the silent mating-type locus HML, for sporulation, and for entry into G. Recombinant ARD1 (amino acids 1-574) or its RING finger domain (amino acids 1-11) produced polyubiquitylated proteins when incubated in vitro with a mammalian E1, an E2 enzyme, ATP, and ubiquitin.