Crystal structure of the maltose transporter in a pretranslocation intermediate state

Science. 2011 Jun 3;332(6034):1202-5. doi: 10.1126/science.1200767. Epub 2011 May 12.


Adenosine triphosphate (ATP)-binding cassette (ABC) transporters convert chemical energy from ATP hydrolysis to mechanical work for substrate translocation. They function by alternating between two states, exposing the substrate-binding site to either side of the membrane. A key question that remains to be addressed is how substrates initiate the transport cycle. Using x-ray crystallography, we have captured the maltose transporter in an intermediate step between the inward- and outward-facing states. We show that interactions with substrate-loaded maltose-binding protein in the periplasm induce a partial closure of the MalK dimer in the cytoplasm. ATP binding to this conformation then promotes progression to the outward-facing state. These results, interpreted in light of biochemical and functional studies, provide a structural basis to understand allosteric communication in ABC transporters.

Publication types

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

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry*
  • ATP-Binding Cassette Transporters / metabolism
  • Adenosine Triphosphate / metabolism
  • Amino Acid Motifs
  • Binding Sites
  • Biological Transport, Active
  • Catalytic Domain
  • Crystallization
  • Crystallography, X-Ray
  • Escherichia coli / chemistry*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Hydrogen Bonding
  • Maltose / metabolism
  • Maltose-Binding Proteins / chemistry
  • Maltose-Binding Proteins / metabolism
  • Models, Biological
  • Models, Molecular
  • Monosaccharide Transport Proteins / chemistry*
  • Monosaccharide Transport Proteins / metabolism
  • Periplasm / metabolism
  • Protein Conformation
  • Protein Multimerization
  • Protein Structure, Secondary
  • Protein Structure, Tertiary


  • ATP-Binding Cassette Transporters
  • Escherichia coli Proteins
  • MalF protein, E coli
  • MalG protein, E coli
  • MalK protein, E coli
  • Maltose-Binding Proteins
  • Monosaccharide Transport Proteins
  • maltose transport system, E coli
  • Maltose
  • Adenosine Triphosphate

Associated data

  • PDB/3PUY
  • PDB/3PUZ
  • PDB/3PV0