Transmembrane Signaling in the Maltose ABC Transporter MalFGK(2)-E PERIPLASMIC MalF-P2 LOOP COMMUNICATES SUBSTRATE AVAILABILITY TO THE ATP-BOUND MalK DIMER

Autor(en): Grote, Mathias
Polyhach, Yevhen
Jeschke, Gunnar
Steinhoff, Heinz-Juergen 
Schneider, Erwin 
Bordignon, Enrica
Stichwörter: BINDING CASSETTE TRANSPORTER; Biochemistry & Molecular Biology; CATALYTIC CYCLE; COMPLEX; ELECTRON-PARAMAGNETIC-RESONANCE; ESCHERICHIA-COLI; INTERACTS; P2; PROTEIN MALE; SALMONELLA; TYPHIMURIUM
Erscheinungsdatum: 2009
Herausgeber: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Journal: JOURNAL OF BIOLOGICAL CHEMISTRY
Volumen: 284
Ausgabe: 26
Startseite: 17521
Seitenende: 17526
Zusammenfassung: 
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 (MalFGK(2)-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 MalK(2), 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.
ISSN: 00219258
DOI: 10.1074/jbc.M109.006270

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