IUBMB Enzyme Nomenclature


Accepted name: ABC-type lipid A-core oligosaccharide transporter

Reaction: ATP + H2O + lipid A-core oligosaccharide[side 1] = ADP + phosphate + lipid A-core oligosaccharide[side 2]

Other name(s): MsbA; lipid flippase; ATP-dependent lipid A-core flippase

Systematic name: ATP phosphohydrolase (ABC-type, lipid A-core oligosaccharide-translocating)

Comments: An ATP-binding cassette (ABC) type transporter, characterized by the presence of two similar ATP-binding domains/proteins and two integral membrane domains/proteins. The enzyme, best characterized from the bacterium Escherichia coli, is located in the inner membrane and mediates the movement of lipid A attached to the core oligosaccharide from the cytoplasm to the periplasmic side of the inner membrane, an important step in the lipopolysaccharide biosynthetic pathway. Not to be confused with EC, ABC-type lipopolysaccharide transporter (LptB), which is implicated in the translocation of LPS from the inner membrane to the outer membrane and acts later in the process.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Karow, M. and Georgopoulos, C. The essential Escherichia coli msbA gene, a multicopy suppressor of null mutations in the htrB gene, is related to the universally conserved family of ATP-dependent translocators. Mol. Microbiol. 7 (1993) 69-79. [PMID: 8094880]

2. Zhou, Z., White, K.A., Polissi, A., Georgopoulos, C. and Raetz, C.R. Function of Escherichia coli MsbA, an essential ABC family transporter, in lipid A and phospholipid biosynthesis. J. Biol. Chem 273 (1998) 12466-12475. [PMID: 9575204]

3. Singh, H., Velamakanni, S., Deery, M.J., Howard, J., Wei, S.L. and van Veen, H.W. ATP-dependent substrate transport by the ABC transporter MsbA is proton-coupled. Nat Commun 7 (2016) 12387. [PMID: 27499013]

[EC created 2018]

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