title: Inducer exclusion in Firmicutes: insights into the regulation of a carbohydrate ATP binding cassette transporter from Lactobacillus casei BL23 by the signal transducing protein P-Ser46-HPr.
abstract: Catabolite repression is a mechanism that enables bacteria to control carbon utilization. As part of this global regulatory network, components of the phosphoenolpyruvate:carbohydrate phosphotransferase system inhibit the uptake of less favorable sugars when a preferred carbon source such as glucose is available. This process is termed inducer exclusion. In bacteria belonging to the phylum Firmicutes, HPr, phosphorylated at serine 46 (P-Ser46-HPr) is the key player but its mode of action is elusive. To address this question at the level of purified protein components, we have chosen a homolog of the Escherichia coli maltose/maltodextrin ATP-binding cassette transporter from Lactobacillus casei (MalE1-MalF1G1K12) as a model system. We show that the solute binding protein, MalE1, binds linear and cyclic maltodextrins but not maltose. Crystal structures of MalE1 complexed with these sugars provide a clue why maltose is not a substrate. P-Ser46-HPr inhibited MalE1/maltotetraose-stimulated ATPase activity of the transporter incorporated in proteoliposomes. Furthermore, cross-linking experiments revealed that P-Ser46-HPr contacts the nucleotide-binding subunit, MalK1, in proximity to the Walker A motif. However, P-Ser46-HPr did not block binding of ATP to MalK1. Together, our findings provide first biochemical evidence that P-Ser-HPr arrests the transport cycle by preventing ATP hydrolysis at the MalK1 subunits of the transporter.
authors.affiliation: Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Homburg
authors.affiliation: Institut für Biologie/Strukturbiologie und Biochemie, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bommer
authors.affiliation: Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Steven
authors.initials: S
authors.lastname: Wuttge
authors.affiliation: Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Carolin
authors.initials: C
authors.lastname: Hobe
authors.affiliation: Institut für Chemie/Angewandte Analytik und Umweltchemie, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Beck
authors.affiliation: Institut für Biologie/Strukturbiologie und Biochemie, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Dobbek
authors.affiliation: Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, F-78350, France.|Expression Génétique Microbienne, Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique, UMR8261, Paris, F-75005, France.
authors.forename: Josef
authors.initials: J
authors.lastname: Deutscher
authors.affiliation: Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Licht
authors.affiliation: Institut für Biologie/Physiologie der Mikroorganismen, Humboldt-Universität zu Berlin, Berlin, D-10099, Germany.
authors.forename: Erwin
authors.identifier: 0000-0002-2980-3208
authors.initials: E
authors.lastname: Schneider
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D000068536:Bacillota / Q000378:metabolism*; D007780:Lacticaseibacillus casei / Q000235:genetics / Q000378:metabolism; D008320:Maltose / Q000031:analogs & derivatives / Q000378:metabolism; D016296:Mutagenesis; D009154:Mutation; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012694:Serine; D015398:Signal Transduction
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D012694:Serine; D008320:Maltose; C009819:maltotetraose; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr