Limits...
Functional Activation of the Flagellar Type III Secretion Export Apparatus.

Phillips AM, Calvo RA, Kearns DB - PLoS Genet. (2015)

Bottom Line: Flagella are assembled sequentially from the inside-out with morphogenetic checkpoints that enforce the temporal order of subunit addition.Genetic suppressor analysis indicates that SwrB activates the flagellar type III secretion export apparatus by the membrane protein FliP.We conclude that SwrB enhances the probability that the flagellar basal body adopts a conformation proficient for secretion to ensure that rod and hook subunits are not secreted in the absence of a suitable platform on which to polymerize.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Indiana University, Bloomington, Indiana, United States of America.

ABSTRACT
Flagella are assembled sequentially from the inside-out with morphogenetic checkpoints that enforce the temporal order of subunit addition. Here we show that flagellar basal bodies fail to proceed to hook assembly at high frequency in the absence of the monotopic protein SwrB of Bacillus subtilis. Genetic suppressor analysis indicates that SwrB activates the flagellar type III secretion export apparatus by the membrane protein FliP. Furthermore, mutants defective in the flagellar C-ring phenocopy the absence of SwrB for reduced hook frequency and C-ring defects may be bypassed either by SwrB overexpression or by a gain-of-function allele in the polymerization domain of FliG. We conclude that SwrB enhances the probability that the flagellar basal body adopts a conformation proficient for secretion to ensure that rod and hook subunits are not secreted in the absence of a suitable platform on which to polymerize.

No MeSH data available.


Related in: MedlinePlus

FliGQ132R rescues hook assembly to a FliM-deficient background.Fluorescence micrographs of the indicated genotypes stained for membranes (FM 4–64, false-colored red) and for the FlgET123C hook variant (Alexa fluor 488 maleimide, false-colored green). The following strains were used to generate this panel: fliM (DK1564), fliM fliGQ132R (DK1476), fliGQ132R (DK1475). Scale bar is 4 μm.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4526659&req=5

pgen.1005443.g008: FliGQ132R rescues hook assembly to a FliM-deficient background.Fluorescence micrographs of the indicated genotypes stained for membranes (FM 4–64, false-colored red) and for the FlgET123C hook variant (Alexa fluor 488 maleimide, false-colored green). The following strains were used to generate this panel: fliM (DK1564), fliM fliGQ132R (DK1476), fliGQ132R (DK1475). Scale bar is 4 μm.

Mentions: The FliGQ132R substitution is located in the central armadillo (ARM) motif associated with polymerization of the rotor and assembly of the FliM C-ring component [32,63,64]. In E. coli and S. enterica, loss-of-function mutations in either the FliG ARM motif or FliM result in assembly defects of extracellular flagellar components [31,34–37,63]. Consistent with a role for FliM in flagellar assembly, mutation of fliM in B. subtilis reduced the flagellar hook frequency similar to that observed in the absence of SwrB (Fig 8). Introduction of the gain-of-function fliGQ132R allele to the fliM mutant background, however, increased hook frequency similar to that found in the isogenic fliGQ132R allele alone (Fig 8). We conclude that the gain-of-function fliGQ132R allele bypasses the absence of FliM and increases the frequency of hook assembly. We infer that FliGQ132R alters the conformation of the flagellar rotor and that this conformation is normally adopted only after complete assembly of FliM into the C-ring.


Functional Activation of the Flagellar Type III Secretion Export Apparatus.

Phillips AM, Calvo RA, Kearns DB - PLoS Genet. (2015)

FliGQ132R rescues hook assembly to a FliM-deficient background.Fluorescence micrographs of the indicated genotypes stained for membranes (FM 4–64, false-colored red) and for the FlgET123C hook variant (Alexa fluor 488 maleimide, false-colored green). The following strains were used to generate this panel: fliM (DK1564), fliM fliGQ132R (DK1476), fliGQ132R (DK1475). Scale bar is 4 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526659&req=5

pgen.1005443.g008: FliGQ132R rescues hook assembly to a FliM-deficient background.Fluorescence micrographs of the indicated genotypes stained for membranes (FM 4–64, false-colored red) and for the FlgET123C hook variant (Alexa fluor 488 maleimide, false-colored green). The following strains were used to generate this panel: fliM (DK1564), fliM fliGQ132R (DK1476), fliGQ132R (DK1475). Scale bar is 4 μm.
Mentions: The FliGQ132R substitution is located in the central armadillo (ARM) motif associated with polymerization of the rotor and assembly of the FliM C-ring component [32,63,64]. In E. coli and S. enterica, loss-of-function mutations in either the FliG ARM motif or FliM result in assembly defects of extracellular flagellar components [31,34–37,63]. Consistent with a role for FliM in flagellar assembly, mutation of fliM in B. subtilis reduced the flagellar hook frequency similar to that observed in the absence of SwrB (Fig 8). Introduction of the gain-of-function fliGQ132R allele to the fliM mutant background, however, increased hook frequency similar to that found in the isogenic fliGQ132R allele alone (Fig 8). We conclude that the gain-of-function fliGQ132R allele bypasses the absence of FliM and increases the frequency of hook assembly. We infer that FliGQ132R alters the conformation of the flagellar rotor and that this conformation is normally adopted only after complete assembly of FliM into the C-ring.

Bottom Line: Flagella are assembled sequentially from the inside-out with morphogenetic checkpoints that enforce the temporal order of subunit addition.Genetic suppressor analysis indicates that SwrB activates the flagellar type III secretion export apparatus by the membrane protein FliP.We conclude that SwrB enhances the probability that the flagellar basal body adopts a conformation proficient for secretion to ensure that rod and hook subunits are not secreted in the absence of a suitable platform on which to polymerize.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Indiana University, Bloomington, Indiana, United States of America.

ABSTRACT
Flagella are assembled sequentially from the inside-out with morphogenetic checkpoints that enforce the temporal order of subunit addition. Here we show that flagellar basal bodies fail to proceed to hook assembly at high frequency in the absence of the monotopic protein SwrB of Bacillus subtilis. Genetic suppressor analysis indicates that SwrB activates the flagellar type III secretion export apparatus by the membrane protein FliP. Furthermore, mutants defective in the flagellar C-ring phenocopy the absence of SwrB for reduced hook frequency and C-ring defects may be bypassed either by SwrB overexpression or by a gain-of-function allele in the polymerization domain of FliG. We conclude that SwrB enhances the probability that the flagellar basal body adopts a conformation proficient for secretion to ensure that rod and hook subunits are not secreted in the absence of a suitable platform on which to polymerize.

No MeSH data available.


Related in: MedlinePlus