title: Substrate transport activation is mediated through second periplasmic loop of transmembrane protein MalF in maltose transport complex of Escherichia coli.
abstract: In a recent study we described the second periplasmic loop P2 of the transmembrane protein MalF (MalF-P2) of the maltose ATP-binding cassette transporter (MalFGK(2)-E) as an important element in the recognition of substrate by the maltose-binding protein MalE. In this study, we focus on MalE and find that MalE undergoes a structural rearrangement after addition of MalF-P2. Analysis of residual dipolar couplings (RDCs) shows that binding of MalF-P2 induces a semiopen state of MalE in the presence and absence of maltose, whereas maltose is retained in the binding pocket. These data are in agreement with paramagnetic relaxation enhancement experiments. After addition of MalF-P2, an increased solvent accessibility for residues in the vicinity of the maltose-binding site of MalE is observed. MalF-P2 is thus not only responsible for substrate recognition, but also directly involved in activation of substrate transport. The observation that substrate-bound and substrate-free MalE in the presence of MalF-P2 adopts a similar semiopen state hints at the origin of the futile ATP hydrolysis of MalFGK(2)-E.
authors.affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany; Helmholtz-Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Tomas
authors.initials: T
authors.lastname: Jacso
authors.affiliation: Institut für Biologie, AG Bakterienphysiologie, Humboldt-Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany.
authors.forename: Erwin
authors.initials: E
authors.lastname: Schneider
authors.affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Rupp
authors.affiliation: Leibniz-Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin-Buch, Germany; Helmholtz-Zentrum München, Deutsches Forschungszentrum für Gesundheit und Umwelt, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany; Center for Integrated Protein Science Munich at Department Chemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany. Electronic address: reif@tum.de.
authors.forename: Bernd
authors.initials: B
authors.lastname: Reif
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001693:Biological Transport, Active; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008320:Maltose / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013379:Substrate Specificity
chemical_list: D018528:ATP-Binding Cassette Transporters; D029968:Escherichia coli Proteins; C461639:MalF protein, E coli; D009004:Monosaccharide Transport Proteins; D008320:Maltose