Structure and mechanism of the S component of a bacterial ECF transporter

Nature. 2010 Dec 2;468(7324):717-20. doi: 10.1038/nature09488. Epub 2010 Oct 24.


The energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters. Each ECF transporter contains a membrane-embedded, substrate-binding protein (known as the S component), an energy-coupling module that comprises two ATP-binding proteins (known as the A and A' components) and a transmembrane protein (known as the T component). The structure and transport mechanism of the ECF family remain unknown. Here we report the crystal structure of RibU, the S component of the ECF-type riboflavin transporter from Staphylococcus aureus at 3.6-Å resolution. RibU contains six transmembrane segments, adopts a previously unreported transporter fold and contains a riboflavin molecule bound to the L1 loop and the periplasmic portion of transmembrane segments 4-6. Structural analysis reveals the essential ligand-binding residues, identifies the putative transport path and, with sequence alignment, uncovers conserved structural features and suggests potential mechanisms of action among the ECF transporters.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Conserved Sequence
  • Crystallography, X-Ray
  • Ligands
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / classification
  • Membrane Transport Proteins / metabolism*
  • Models, Molecular
  • Movement
  • Periplasm / metabolism
  • Protein Folding
  • Protein Structure, Tertiary
  • Riboflavin / chemistry
  • Riboflavin / metabolism*
  • Sequence Alignment
  • Staphylococcus aureus / chemistry*
  • Substrate Specificity


  • Bacterial Proteins
  • Ligands
  • Membrane Transport Proteins
  • Riboflavin

Associated data

  • PDB/3CHX
  • PDB/3P5N