The bacterial flagellar switch complex is getting more complex.
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.
Cohen-Ben-Lulu
Galit N
GN
Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel.
Francis
Noreen R
NR
Shimoni
Eyal
E
Noy
Dror
D
Davidov
Yaacov
Y
Prasad
Krishna
K
Sagi
Yael
Y
Cecchini
Gary
G
Johnstone
Rose M
RM
Eisenbach
Michael
M
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
D001426:Bacterial Proteins; C075660:Flig protein, Bacteria; D005650:Fumarates; D011993:Recombinant Fusion Proteins; C032005:fumaric acid; D013385:Succinate Dehydrogenase