A tweezers-like motion of the ATP-binding cassette dimer in an ABC transport cycle

Mol Cell. 2003 Sep;12(3):651-61. doi: 10.1016/j.molcel.2003.08.004.


The ATPase components of ATP binding cassette (ABC) transporters power the transporters by binding and hydrolyzing ATP. Major conformational changes of an ATPase are revealed by crystal structures of MalK, the ATPase subunit of the maltose transporter from Escherichia coli, in three different dimeric configurations. While other nucleotide binding domains or subunits display low affinity for each other in the absence of the transmembrane segments, the MalK dimer is stabilized through interactions of the additional C-terminal domains. In the two nucleotide-free structures, the N-terminal nucleotide binding domains are separated to differing degrees, and the dimer is maintained through contacts of the C-terminal regulatory domains. In the ATP-bound form, the nucleotide binding domains make contact and two ATPs lie buried along the dimer interface. The two nucleotide binding domains of the dimer open and close like a pair of tweezers, suggesting a regulatory mechanism for ATPase activity that may be tightly coupled to translocation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP-Binding Cassette Transporters / metabolism*
  • Adenosine Triphosphatases / metabolism
  • Amino Acid Sequence / physiology
  • Animals
  • Bacterial Proteins / metabolism
  • Binding Sites / physiology
  • Biological Transport, Active / physiology*
  • Cell Membrane / metabolism*
  • Dimerization
  • Escherichia coli Proteins*
  • Eukaryotic Cells / metabolism*
  • Humans
  • Intracellular Membranes / metabolism*
  • Models, Molecular
  • Molecular Conformation
  • Molecular Sequence Data
  • Nucleotides / metabolism
  • Protein Structure, Tertiary / physiology
  • Protein Subunits / metabolism


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Escherichia coli Proteins
  • MalK protein, Bacteria
  • MalK protein, E coli
  • Nucleotides
  • Protein Subunits
  • Adenosine Triphosphatases

Associated data

  • PDB/1Q12
  • PDB/1Q1B
  • PDB/1Q1E