Inter-domain communication mechanisms in an ABC importer: a molecular dynamics study of the MalFGK2E complex

PLoS Comput Biol. 2011 Aug;7(8):e1002128. doi: 10.1371/journal.pcbi.1002128. Epub 2011 Aug 4.

Abstract

ATP-Binding Cassette transporters are ubiquitous membrane proteins that convert the energy from ATP-binding and hydrolysis into conformational changes of the transmembrane region to allow the translocation of substrates against their concentration gradient. Despite the large amount of structural and biochemical data available for this family, it is still not clear how the energy obtained from ATP hydrolysis in the ATPase domains is "transmitted" to the transmembrane domains. In this work, we focus our attention on the consequences of hydrolysis and inorganic phosphate exit in the maltose uptake system (MalFGK(2)E) from Escherichia coli. The prime goal is to identify and map the structural changes occurring during an ATP-hydrolytic cycle. For that, we use extensive molecular dynamics simulations to study three potential intermediate states (with 10 replicates each): an ATP-bound, an ADP plus inorganic phosphate-bound and an ADP-bound state. Our results show that the residues presenting major rearrangements are located in the A-loop, in the helical sub-domain, and in the "EAA motif" (especially in the "coupling helices" region). Additionally, in one of the simulations with ADP we were able to observe the opening of the NBD dimer accompanied by the dissociation of ADP from the ABC signature motif, but not from its corresponding P-loop motif. This work, together with several other MD studies, suggests a common communication mechanism both for importers and exporters, in which ATP-hydrolysis induces conformational changes in the helical sub-domain region, in turn transferred to the transmembrane domains via the "coupling helices".

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry*
  • ATP-Binding Cassette Transporters / metabolism
  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Amino Acid Motifs
  • Crystallography, X-Ray
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Hydrolysis
  • Maltose / chemistry
  • Maltose / metabolism
  • Molecular Dynamics Simulation*
  • Protein Conformation
  • Protein Structure, Tertiary
  • Signal Transduction

Substances

  • ATP-Binding Cassette Transporters
  • Escherichia coli Proteins
  • maltose transport system, E coli
  • Adenosine Diphosphate
  • Maltose
  • Adenosine Triphosphate