Flagellar assembly in Caulobacter crescentus: a basal body P-ring null mutation affects stability of the L-ring protein.
The P- and L-rings are structural components of the flagellar basal body that are positioned in the periplasmic space and outer membrane, respectively. In order to explore the mechanism of P- and L-ring assembly, we examined the effect of a null mutation in the gene encoding the P-ring subunit, FlgI, on the expression, stability, and subcellular localization of the L-ring subunit, FlgH, in Caulobacter crescentus. Transcription of the L-ring gene and synthesis of the L-ring protein were both increased in the P-ring null mutant. However, steady-state L-ring protein levels were dramatically reduced compared with those of wild type. This reduction, which was not observed in flagellar hook mutants, was due to a decreased stability of the L-ring protein. The instability of the L-ring protein was apparent throughout the cell cycle of the P-ring mutant and contrasted with the fairly constant level of L-ring protein during the cell cycle of wild-type cells. Low levels of the L-ring protein were detected exclusively in the cell envelope of cells lacking the P-ring, suggesting that, in the absence of P-ring assembly, L-ring monomers are unable to form multimeric rings and are thus subject to proteolysis in the periplasm.
Department of Developmental Biology, Beckman Center, Stanford University School of Medicine, California 94305-5427, USA.
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Mohr
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Jenal
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Shapiro
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016935:Caulobacter crescentus / Q000737:chemistry*; D005407:Flagella / Q000737:chemistry*; D009154:Mutation; D014158:Transcription, Genetic
D001426:Bacterial Proteins