5nik | pdb_00005nik

Structure of the MacAB-TolC ABC-type tripartite multidrug efflux pump

Loading... Status: waiting for Mol* initialization Structural highlights 5nik is a 11 chain structure with sequence from Ecoli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Gene: tolC, colE1-i, mtcB, mukA, refI, toc, weeA, b3035, JW5503 (ECOLI), macA, ybjY, b0878, JW0862 (ECOLI), macB, ybjZ, b0879, JW0863 (ECOLI) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [TOLC_ECOLI] Outer membrane channel, which is required for the function of several efflux systems such as AcrAB-TolC, AcrEF-TolC, EmrAB-TolC and MacAB-TolC. These systems are involved in export of antibiotics and other toxic compounds from the cell. TolC is also involved in import of colicin E1 into the cells. [MACB_ECOLI] Part of the tripartite efflux system MacAB-TolC. MacB is a non-canonical ABC transporter that contains transmembrane domains (TMD), which form a pore in the inner membrane, and an ATP-binding domain (NBD), which is responsible for energy generation. When overexpressed, the system confers resistance against macrolides composed of 14- and 15-membered lactones but no or weak resistance against 16-membered ones. In addition, the system could also transport R-LPS or a similar glycolipid. [MACA_ECOLI] Part of the tripartite efflux system MacAB-TolC. MacA stimulates the ATPase activity of MacB by promoting the closed ATP-bound state of MacB, increases the capacity of MacB to bind macrolides such as erythromycin, and provides a physical link between MacB and TolC. When overexpressed, the system confers resistance against macrolides composed of 14- and 15-membered lactones but no or weak resistance against 16-membered ones. In addition, MacA binds tightly rough-core lipopolysaccharide (R-LPS), suggesting that the system could also transport R-LPS or a similar glycolipid. Publication Abstract from PubMed The MacA-MacB-TolC assembly of Escherichia coli is a transmembrane machine that spans the cell envelope and actively extrudes substrates, including macrolide antibiotics and polypeptide virulence factors. These transport processes are energized by the ATPase MacB, a member of the ATP-binding cassette (ABC) superfamily. We present an electron cryo-microscopy structure of the ABC-type tripartite assembly at near-atomic resolution. A hexamer of the periplasmic protein MacA bridges between a TolC trimer in the outer membrane and a MacB dimer in the inner membrane, generating a quaternary structure with a central channel for substrate translocation. A gating ring found in MacA is proposed to act as a one-way valve in substrate transport. The MacB structure features an atypical transmembrane domain with a closely packed dimer interface and a periplasmic opening that is the likely portal for substrate entry from the periplasm, with subsequent displacement through an allosteric transport mechanism. Structure of the MacAB-TolC ABC-type tripartite multidrug efflux pump.,Fitzpatrick AWP, Llabres S, Neuberger A, Blaza JN, Bai XC, Okada U, Murakami S, van Veen HW, Zachariae U, Scheres SHW, Luisi BF, Du D Nat Microbiol. 2017 May 15;2:17070. doi: 10.1038/nmicrobiol.2017.70. PMID:28504659 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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