Acyl Carrier Protein (ACP)

Acyl carrier protein (ACP) plays an important role in fatty acid and polyketide biosynthesis as an essential cofactor. It is one of the most abundant proteins in cells of E. coli. ACP is covalently attached to the acyl intermediates of fatty acid biosynthesis and directs them into the synthetic pathway. The intermediate is linked via the terminal sulfhydryl of the 4′-phosphopantetheine group, which is in turn attached to ACP through a phosphodiester bond to a conserved Ser residue. Apo-ACP is inactive as an acyl carrier, and it is converted to the active holo form by holo-(ACP) synthase (AcpS), which transfers the 4′-phosphopantetheine group from CoA to ACP.

The structure of ACP affect fatty acid or polyketide biosynthetic reactions. It is a small, highly soluble protein composed of four α-helices with a high degree of structural and amino acid similarity. Scientists have investigated the structures of ACP by using various NMR and crystallographic techniques, from a number of sources. Structurally and mechanistically, ACP is related to the peptidyl carrier protein (PCP) of nonribosomal peptide synthases.