A Molecular Mechanism of Bacterial Flagellar Motor Switching

Dyer, Collin M.; Vartanian, Armand S.; Zhou, Hongjun; Dahlquist, Frederick W.

doi:10.1016/j.jmb.2009.02.004

Cited by 69 publications

(92 citation statements)

References 58 publications

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“…Both of these proteins function in controlling the direction of flagellar rotation (50)(51)(52)(53), and single point mutations in FliM have been shown to restore swarming motility in a chemotaxis-deficient mutant of Salmonella enterica (52). We hypothesize that SNPs in these genes led to enhanced swarming motility of the corresponding revertants by direct manipulation of the flagellar motor.…”

Section: Resultsmentioning

confidence: 95%

A prl Mutation in SecY Suppresses Secretion and Virulence Defects of Listeria monocytogenes secA2 Mutants

2015

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The bulk of bacterial protein secretion occurs through the conserved SecY translocation channel that is powered by SecA-dependent ATP hydrolysis. Many Gram-positive bacteria, including the human pathogen Listeria monocytogenes, possess an additional nonessential specialized ATPase, SecA2. SecA2-dependent secretion is required for normal cell morphology and virulence in L. monocytogenes; however, the mechanism of export via this pathway is poorly understood. L. monocytogenes secA2 mutants form rough colonies, have septation defects, are impaired for swarming motility, and form small plaques in tissue culture cells. In this study, 70 spontaneous mutants were isolated that restored swarming motility to L. monocytogenes secA2 mutants. Most of the mutants had smooth colony morphology and septated normally, but all were lysozyme sensitive. Five representative mutants were subjected to whole-genome sequencing. Four of the five had mutations in proteins encoded by the lmo2769 operon that conferred lysozyme sensitivity and increased swarming but did not rescue virulence defects. A point mutation in secY was identified that conferred smooth colony morphology to secA2 mutants, restored wild-type plaque formation, and increased virulence in mice. This secY mutation resembled a prl suppressor known to expand the repertoire of proteins secreted through the SecY translocation complex. Accordingly, the ⌬secA2prlA1 mutant showed wild-type secretion levels of P60, an established SecA2-dependent secreted autolysin. Although the prl mutation largely suppressed almost all of the measurable SecA2-dependent traits, the ⌬secA2prlA1 mutant was still less virulent in vivo than the wild-type strain, suggesting that SecA2 function was still required for pathogenesis.T he essential general secretory (Sec) pathway is responsible for exporting the majority of secreted proteins across the bacterial cell membrane (1-3). Much of what we know about this pathway was discovered in Escherichia coli by using genetic screens to identify loss-of-function mutations in components of the Sec system. This led to the identification of components of the SecYEG complex that forms the translocation channel and the SecA ATPase that binds to signal sequences to drive the export of precursor proteins across the channel (3-9). In contrast to loss-of-function sec mutations, prl alleles are gain-of-function mutations, which expand the repertoire of substrates being exported across the SecYEG channel (6-8, 10, 11). The most dominant prl variants are in secY, known as prlA mutations, which allow for the secretion of proteins with altered signal sequence (7, 9, 11) without significantly altering the secretion of other proteins (6,12).In addition to the canonical SecA, an accessory cytosolic ATPase, SecA2, has been identified in Mycobacterium and a subset of other Gram-positive bacteria. Unlike SecA, SecA2 is not essential for cell viability but is required for virulence in some pathogenic bacteria (13-15). SecA1 and SecA2 are homologous but are not interchangeable (16)...

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Section: Resultsmentioning

confidence: 95%

A prl Mutation in SecY Suppresses Secretion and Virulence Defects of Listeria monocytogenes secA2 Mutants

2015

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“…FliM contains an amino-terminal CheY-binding motif (FliMn) that recruits CheY-P to the motor (25)(26)(27). NMR studies have shown that in addition to CheY-P binding to the N-terminal motif, it also interacts with the middle domain of FliM, albeit weakly (29). The crystal structure of the middle domain of FliM (FliMm) reveals a topology similar to CheC (30).…”

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Structure and Activity of the Flagellar Rotor Protein FliY

Sircar

Greenswag

Bilwes

et al. 2013

Journal of Biological Chemistry

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“…In most species, the motor can rotate either clockwise (CW) or counterclockwise (CCW), and cells can direct their movement toward favorable environments or away from unfavorable ones by controlling the direction of motor rotation (1)(2)(3)(4). The molecular mechanism of the motor is not understood fully, but proteins with key roles in rotation and direction switching have been identified, and some general aspects of the mechanism have been established (5,6).…”

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A molecular mechanism of direction switching in the flagellar motor of Escherichia coli

Paul

Brunstetter

Titen

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The direction of flagellar rotation is regulated by a rotor-mounted protein assembly, termed the "switch complex," formed from multiple copies of the proteins FliG, FliM, and FliN. The structures of major parts of these proteins are known, and the overall organization of proteins in the complex has been elucidated previously using a combination of protein-binding, mutational, and crosslinking approaches. In Escherichia coli, the switch from counterclockwise to clockwise rotation is triggered by the signaling protein phospho-CheY, which binds to the lower part of the switch complex and induces small movements of FliM and FliN subunits relative to each other. Direction switching also must produce movements in the upper part of the complex, particularly in the C-terminal domain of FliG (FliG C ), which interacts with the stator to generate the torque for flagellar rotation. In the present study, protein movements in the middle and upper parts of the switch complex have been probed by means of targeted cross-linking and mutational analysis. Switching induces a tilting movement of the FliM domains that form the middle part of the switch and a consequent rotation of the affixed FliG C domains that reorients the stator interaction sites by about 908. In a recently proposed hypothesis for the motor mechanism, such a reorientation of FliG C would reverse the direction of motor rotation. molecular machines | motility | signal transduction

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A Molecular Mechanism of Bacterial Flagellar Motor Switching

Cited by 69 publications

References 58 publications

A prl Mutation in SecY Suppresses Secretion and Virulence Defects of Listeria monocytogenes secA2 Mutants

A prl Mutation in SecY Suppresses Secretion and Virulence Defects of Listeria monocytogenes secA2 Mutants

Structure and Activity of the Flagellar Rotor Protein FliY

A molecular mechanism of direction switching in the flagellar motor of Escherichia coli

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