title: The bacterial flagellar switch complex is getting more complex.
abstract: The mechanism of function of the bacterial flagellar switch, which determines the direction of flagellar rotation and is essential for chemotaxis, has remained an enigma for many years. Here we show that the switch complex associates with the membrane-bound respiratory protein fumarate reductase (FRD). We provide evidence that FRD binds to preparations of isolated switch complexes, forms a 1:1 complex with the switch protein FliG, and that this interaction is required for both flagellar assembly and switching the direction of flagellar rotation. We further show that fumarate, known to be a clockwise/switch factor, affects the direction of flagellar rotation through FRD. These results not only uncover a new component important for switching and flagellar assembly, but they also reveal that FRD, an enzyme known to be primarily expressed and functional under anaerobic conditions in Escherichia coli, nonetheless, has important, unexpected functions under aerobic conditions.
authors.affiliation: Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Galit N
authors.initials: GN
authors.lastname: Cohen-Ben-Lulu
authors.forename: Noreen R
authors.initials: NR
authors.lastname: Francis
authors.forename: Eyal
authors.initials: E
authors.lastname: Shimoni
authors.forename: Dror
authors.initials: D
authors.lastname: Noy
authors.forename: Yaacov
authors.initials: Y
authors.lastname: Davidov
authors.forename: Krishna
authors.initials: K
authors.lastname: Prasad
authors.forename: Yael
authors.initials: Y
authors.lastname: Sagi
authors.forename: Gary
authors.initials: G
authors.lastname: Cecchini
authors.forename: Rose M
authors.initials: RM
authors.lastname: Johnstone
authors.forename: Michael
authors.initials: M
authors.lastname: Eisenbach
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D005407:Flagella / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D005650:Fumarates / Q000378:metabolism; D017353:Gene Deletion; D005812:Genes, Switch; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C075660:Flig protein, Bacteria; D005650:Fumarates; D011993:Recombinant Fusion Proteins; C032005:fumaric acid; D013385:Succinate Dehydrogenase