Identification and characterization of FliY, a novel component of the Bacillus subtilis flagellar switch complex

Abstract

The Bacillus subtilis gene encoding FliY has been cloned and sequenced. The gene encodes a 379-amino-acid protein with a predicted molecular mass of 41,054 daltons. FliY is partly homologous to the Escherichia coli and Salmonella typhimurium switch proteins FliM and FliN. The N-terminus of FliY has 33% identity with the first 122 amino acids of FliM, whereas the C-terminus of FliY has 52% identity with the last 30 amino acids of FliN. The middle 60% of FliY is not significantly homologous to either of the proteins. A fliY::cat null mutant has no flagella. Motility can be restored to the mutant by expression of fliY from a plasmid, although chemotaxis is still defective since the strain exhibits smooth swimming behaviour. fliY::cat is in the cheD complementation group. One of the cheD point mutants does not switch although the population grown from a single cell has both smooth swimming and tumbling bacteria, implying that the switch is locked. Expression of fliY in wild-type B. subtilis makes the cells more smooth-swimming but does not appear to affect chemotaxis. Expression of fliY in wild-type S. typhimurium severely inhibits chemotaxis and also makes the cells smooth swimming. Expression in a non-motile S. typhimurium fliN mutant restores motility but not chemotaxis, although expression in a non-motile E. coli fliM mutant does not restore motility. The homology, multiple phenotypes, and interspecies complementation suggest that FliY forms part of the B. subtilis switch complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Swarming motility in Bacillus cereus and characterization of a fliY mutant impaired in swarm cell differentiation The EMBL accession number for the sequence reported in this paper is Y08031.

“…P24073 ; 40 % identity in 173 overlapping amino acids, 46 % of FliY). The protein encoded by fliY (FliY) in B. subtilis is an essential component of the flagellar motor-switch complex (C-ring) and represents the Gram-positive counterpart of the Gram-negative FliN (Bischoff & Ordal, 1992). iments with the chromosomal DNA derived from strains NCIB 8122 and MP01.…”

“…Spreading of B. cereus, briefly discussed in a general review on bacterial surface translocation (Henrichsen, 1972), has been reported to be due to swimming motility only, brought about by individual cells that do not exhibit hyperflagellation or elongation. In this report, we demonstrate that B. cereus is capable of swarming differentiation and that the production of differentiated swarm cells requires the activity of fliY (Celandroni et al, 2000), the homologue of which in Bacillus subtilis encodes an essential component of the flagellar-switch complex (C-ring) controlling the direction of flagellum rotation (Bischoff & Ordal, 1992). Complementation of a fliY deletion, identified in a motile but non-swarming and non-chemotactic spontaneous mutant of B. cereus, restores the ability to produce differentiated swarm cells as well as to respond to chemoattractants.…”

Bacillus subtilis Hydrolyzes CheY-P at the Location of Its Action, the Flagellar Switch

“…Its genome revealed a FliY-like protein (coordinates 706,930 -707,957) (25), which through an (authentic) frameshift appears to be cut into two proteins, a FliY N-terminal part and a FliN. It appears likely that the FliN part is actually expressed as both S. typhimurium fliN and B. subtilis fliY mutants are not flagellated (11,12), yet T. maritima MSB8 is motile (26) and its genome does not seem to encode for an alternative FliN. This might be an example of how FliN originated from FliY by loss of its N-terminal domain.…”

“…1A) (7). The fact that a Salmonella typhimurium fliN mutant could be partially complemented by B. subtilis fliY indicates that these two proteins share a common function as a component of the flagellar switch (11).…”

“…FliM has been shown to directly interact with CheY-P and induce change of direction of flagellar rotation (10). B. subtilis has the orthologs FliM and FliG, but instead of FliN has FliY, which is homologous to FliN only in its C terminus (11). Its N-terminal domain is homologous to CheC (27% of residues identical, 48% similar) ( Fig.…”