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RcsA, an unstable positive regulator of capsular polysaccharide synthesis.

ABSTRACT: RcsA is an unstable positive regulator required for the synthesis of colanic acid capsular polysaccharide in Escherichia coli. Degradation of the RcsA protein in vivo depends on the ATP-dependent Lon protease. DNA sequence analysis of the rcsA gene reveals a single open reading frame for a 23,500-Da highly basic protein (pI = 9.9), consistent with the observed size of the purified subunit of RcsA. The DNA and protein sequences are highly homologous to the rcsA gene and protein from Klebsiella pneumoniae and other species. The carboxy-terminal region of RcsA contains a possible helix-turn-helix DNA-binding motif that resembles sequences found at the carboxy terminus of RcsB, another positive regulator of capsule synthesis, and in several other transcriptional regulators including members of the LuxR family. rcsA62, a mutation in rcsA that leads to increased capsule synthesis, encodes a protein designated RcsA*, which differs from wild-type RcsA only in the replacement of Met-145 by valine. The RcsA* protein is subject to Lon-dependent degradation. The stability of wild-type RcsA in vivo is increased by multicopy RcsB. Conversely, RcsA is degraded more rapidly in rcsB mutant hosts than in wild-type hosts. These results suggest that RcsA and RcsB interact in vivo and are consistent with genetic experiments that indicate an interaction between RcsA and RcsB. Based on these experiments, we propose a model for capsule regulation in which RcsA interacts directly with RcsB to promote transcription of the genes for capsule synthesis.

SUBMITTER: Stout V

PROVIDER: S-EPMC207325 | biostudies-other | 1991 Mar

REPOSITORIES: biostudies-other

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RcsA, an unstable positive regulator of capsular polysaccharide synthesis.

Stout V V Torres-Cabassa A A Maurizi M R MR Gutnick D D Gottesman S S

Journal of bacteriology 19910301 5

RcsA is an unstable positive regulator required for the synthesis of colanic acid capsular polysaccharide in Escherichia coli. Degradation of the RcsA protein in vivo depends on the ATP-dependent Lon protease. DNA sequence analysis of the rcsA gene reveals a single open reading frame for a 23,500-Da highly basic protein (pI = 9.9), consistent with the observed size of the purified subunit of RcsA. The DNA and protein sequences are highly homologous to the rcsA gene and protein from Klebsiella pn ...[more]

PMID: 1999391

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Project description:Bacteriophages infecting Tetragenococcus halophilus, a halophilic lactic acid bacterium, have been a major industrial concern due to their detrimental effects on the quality of food products. Previously characterized tetragenococcal phages displayed narrow host ranges, but there is little information on these mechanisms. Here, we revealed the host's determinant factors for phage susceptibility using two virulent phages, phiYA5_2 and phiYG2_4, that infect T. halophilus YA5 and YG2, respectively. Phage-resistant derivatives were obtained from these host strains, and mutations were found at the capsular polysaccharide (CPS) synthesis (cps) loci. Quantification analysis verified that capsular polysaccharide production by the cps derivatives from YG2 was impaired. Transmission electron microscopy observation confirmed the presence of filamentous structures outside the cell walls of YG2 and their absence in the cps derivatives of YG2. Phage adsorption assays revealed that phiYG2_4 adsorbed to YG2 but not its cps derivatives, which suggests that the capsular polysaccharide of YG2 is the specific receptor for phiYG2_4. Interestingly, phiYA5_2 adsorbed and infected cps derivatives of YG2, although neither adsorption to nor infection of the parental strain YG2 by phiYA5_2 was observed. The plaque-surrounding halos formed by phiYA5_2 implied the presence of the virion-associated depolymerase that degrades the capsular polysaccharide of YA5. These results indicated that the capsular polysaccharide is a physical barrier rather than a binding receptor for phiYA5_2 and that phiYA5_2 specifically overcomes the capsular polysaccharide of YA5. Thus, it is suggested that tetragenococcal phages utilize CPSs as binding receptors and/or degrade CPSs to approach host cells. IMPORTANCE T. halophilus is a halophilic lactic acid bacterium that contributes to the fermentation processes for various salted foods. Bacteriophage infections of T. halophilus have been a major industrial problem causing fermentation failures. Here, we identified the cps loci in T. halophilus as genetic determinants of phage susceptibility. The structural diversity of the capsular polysaccharide is responsible for the narrow host ranges of tetragenococcal phages. The information provided here could facilitate future studies on tetragenococcal phages and the development of efficient methods to prevent bacteriophage infections.

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RcsA, an unstable positive regulator of capsular polysaccharide synthesis.

Publications

RcsA, an unstable positive regulator of capsular polysaccharide synthesis.

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