Transmembrane Signaling in the Maltose ABC Transporter MalFGK2-E: PERIPLASMIC MalF-P2 LOOP COMMUNICATES SUBSTRATE AVAILABILITY TO THE ATP-BOUND MalK DIMER*
AUTOR(ES)
Grote, Mathias
FONTE
American Society for Biochemistry and Molecular Biology
RESUMO
ABC transporters are ubiquitous membrane proteins that translocate solutes across biological membranes at the expense of ATP. In prokaryotic ABC importers, the extracytoplasmic anchoring of the substrate-binding protein (receptor) is emerging as a key determinant for the structural rearrangements in the cytoplasmically exposed ATP-binding cassette domains and in the transmembrane gates during the nucleotide cycle. Here the molecular mechanism of such signaling events was addressed by electron paramagnetic resonance spectroscopy of spin-labeled ATP-binding cassette maltose transporter variants (MalFGK2-E). A series of doubly spin-labeled mutants in the MalF-P2 domain involving positions 92, 205, 239, 252, and 273 and one triple mutant labeled at positions 205/252 in P2 and 83 in the Q-loop of MalK were assayed. The EPR data revealed that the substrate-binding protein MalE is bound to the transporter throughout the transport cycle. Concomitantly with the three conformations of the ATP-binding cassette MalK2, three functionally relevant conformations are found also in the periplasmic MalF-P2 loop, strictly dependent on cytoplasmic nucleotide binding and periplasmic docking of liganded MalE to MalFG. The reciprocal communication across the membrane unveiled here gives first insights into the stimulatory effect of MalE on the ATPase activity, and it is suggested to be an important mechanistic feature of receptor-coupled ABC transporters.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2719391Documentos Relacionados
- MalFGK complex assembly and transport and regulatory characteristics of MalK insertion mutants.
- The MalK protein of the ATP-binding cassette transporter for maltose of Escherichia coli is accessible to protease digestion from the periplasmic side of the membrane.
- ATP-Bound Conformation of Topoisomerase IV: a Possible Target for Quinolones in Streptococcus pneumoniae
- Crystal structure of MalK, the ATPase subunit of the trehalose/maltose ABC transporter of the archaeon Thermococcus litoralis
- Enhanced nucleic acid binding to ATP-bound hepatitis C virus NS3 helicase at low pH activates RNA unwinding