Structure of a bacterial energy-coupling factor transporter

Nature. 2013 May 9;497(7448):272-6. doi: 10.1038/nature12045. Epub 2013 Apr 14.


The energy-coupling factor (ECF) transporters constitute a novel family of conserved membrane transporters in prokaryotes that have a similar domain organization to the ATP-binding cassette transporters. Each ECF transporter comprises a pair of cytosolic ATPases (the A and A' components, or EcfA and EcfA'), a membrane-embedded substrate-binding protein (the S component, or EcfS) and a transmembrane energy-coupling component (the T component, or EcfT) that links the EcfA-EcfA' subcomplex to EcfS. The structure and transport mechanism of the quaternary ECF transporter remain largely unknown. Here we report the crystal structure of a nucleotide-free ECF transporter from Lactobacillus brevis at a resolution of 3.5 Å. The T component has a horseshoe-shaped open architecture, with five α-helices as transmembrane segments and two cytoplasmic α-helices as coupling modules connecting to the A and A' components. Strikingly, the S component, thought to be specific for hydroxymethyl pyrimidine, lies horizontally along the lipid membrane and is bound exclusively by the five transmembrane segments and the two cytoplasmic helices of the T component. These structural features suggest a plausible working model for the transport cycle of the ECF transporters.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • Anti-Bacterial Agents
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Crystallography, X-Ray
  • Cytoplasm / chemistry
  • Cytoplasm / metabolism
  • Levilactobacillus brevis / chemistry*
  • Models, Biological
  • Models, Molecular
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • Pyrimidines / chemistry
  • Pyrimidines / metabolism
  • Structure-Activity Relationship
  • Substrate Specificity


  • ATP-Binding Cassette Transporters
  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Protein Subunits
  • Pyrimidines

Associated data

  • PDB/4HZU