On the basis of sequence similarity, a number of transferases have been proposed [1,2,3,4] to belong to a single family. These proteins are:

• Serine O-acetyltransferase (EC 2.3.1.30) (SAT) (gene cysE), an enzyme involved in cysteine biosynthesis.
• Azotobacter chroococcum nitrogen fixation protein nifP. NifP is most probably a SAT involved in the optimization of nitrogenase activity.
• Escherichia coli thiogalactoside acetyltransferase (EC 2.3.1.18) (gene lacA), an enzyme involved in the biosynthesis of lactose.
• UDP-N-acetylglucosamine acyltransferase (EC 2.3.1.129) (gene lpxA), an enzyme involved in the biosynthesis of lipid A, a phosphorylated glycolipid that anchors the lipopolysaccharide to the outer membrane of the cell.
• UDP-3-O-[3-hydroxymyristoyl] glucosamine N-acyltransferase (EC 2.3.1.-) (gene lpxD or firA), which is also involved in the biosynthesis of lipid A.
• Chloramphenicol O-acetyltransferase (CAT) (EC 2.3.1.28) from Agrobacterium tumefaciens, Bacillus sphaericus, Escherichia coli plasmid IncFII NR79, Pseudomonas aeruginosa, Staphylococcus aureus plasmid pIP630. These CAT are not evolutionary related to the main family of CAT (see <PDOC00093>).
• Rhizobium nodulation protein nodL. NodL is an acetyltransferase involved in the O-acetylation of Nod factors.
• Bacterial maltose O-acetyltransferase (EC 2.3.1.79).
• Bacterial tetrahydrodipicolinate N-succinyltransferase (EC 2.3.1.117) (gene dapD) which catalyzes the fourth step in the biosynthesis of diaminopimelate and lysine from aspartate semialdehyde.
• Bacterial N-acetylglucosamine-1-phosphate uridyltransferase (EC 2.7.7.23) (gene glmU or gcaD or tms), an enzyme involved in peptidoglycan and lipopolysaccharide biosynthesis.
• Staphylococcus aureus protein capG which is involved in biosynthesis of type 1 capsular polysaccharide.
• Yeast hypothetical protein YJL218w, which is highly similar to Escherichia coli lacA.
• Fission yeast hypothetical protein SpAC18B11.09c.
• Methanococcus jannaschii hypothetical protein MJ1064.

These proteins have been shown [3,4] to contain a repeat structure composed of tandem repeats of a [LIV]-G-x(4) hexapeptide which, in the tertiary structure of lpxA [5], has been shown to form a left-handed parallel β helix. Our signature pattern is based on a fourfold repeat of this hexapeptide.