7CH6

Cryo-EM structure of E.coli MlaFEB with AMPPNP

Summary for 7CH6

• Entry DOI: 10.2210/pdb7ch6/pdb
• EMDB information: 30369
• Descriptor: Lipid asymmetry maintenance ABC transporter permease subunit MlaE, Phospholipid ABC transporter ATP-binding protein MlaF, Lipid asymmetry maintenance protein MlaB, ... (4 entities in total)
• Functional Keywords: mla complex, lipid transporter, membrane protein
• Biological source: Escherichia coli (strain K12); More
• Total number of polymer chains: 6
• Total formula weight: 136420.94

Authors

Zhou, C.,Shi, H.,Zhang, M.,Huang, Y. (deposition date: 2020-07-05, release date: 2021-08-04, Last modification date: 2024-03-27)

Primary citation

Zhou, C.,Shi, H.,Zhang, M.,Zhou, L.,Xiao, L.,Feng, S.,Im, W.,Zhou, M.,Zhang, X.,Huang, Y.
Structural Insight into Phospholipid Transport by the MlaFEBD Complex from P. aeruginosa.
J.Mol.Biol., 433:166986-166986, 2021

PubMed Abstract: The outer membrane (OM) of Gram-negative bacteria, which consists of lipopolysaccharides (LPS) in the outer leaflet and phospholipids (PLs) in the inner leaflet, plays a key role in antibiotic resistance and pathogen virulence. The maintenance of lipid asymmetry (Mla) pathway is known to be involved in PL transport and contributes to the lipid homeostasis of the OM, yet the underlying molecular mechanism and the directionality of PL transport in this pathway remain elusive. Here, we reported the cryo-EM structures of the ATP-binding cassette (ABC) transporter MlaFEBD from P. areuginosa, the core complex in the Mla pathway, in nucleotide-free (apo)-, ADP (ATP + vanadate)- and ATP (AMPPNP)-bound states as well as the structures of MlaFEB from E. coli in apo- and AMPPNP-bound states at a resolution range of 3.4-3.9 Å. The structures show that the MlaFEBD complex contains a total of twelve protein molecules with a stoichiometry of MlaFEBD, and binds a plethora of PLs at different locations. In contrast to canonical ABC transporters, nucleotide binding fails to trigger significant conformational changes of both MlaFEBD and MlaFEB in the nucleotide-binding and transmembrane domains of the ABC transporter, correlated with their low ATPase activities exhibited in both detergent micelles and lipid nanodiscs. Intriguingly, PLs or detergents appeared to relocate to the membrane-proximal end from the distal end of the hydrophobic tunnel formed by the MlaD hexamer in MlaFEBD upon addition of ATP, indicating that retrograde PL transport might occur in the tunnel in an ATP-dependent manner. Site-specific photocrosslinking experiment confirms that the substrate-binding pocket in the dimeric MlaE and the MlaD hexamer are able to bind PLs in vitro, in line with the notion that MlaFEBD complex functions as a PL transporter.

PubMed: 33845086
DOI: 10.1016/j.jmb.2021.166986

Experimental method

ELECTRON MICROSCOPY (3.4 Å)