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Outer membrane protein a and other polypeptides regulate capsular polysaccharide synthesis in E. coli K-12.

R C Gayda·H Avni·P E Berg·A Markovitz
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Abstract

capR (lon) mutants of Escherichia coli K-12 are mucoid on minimal agar because they produce large quantities of capsular polysaccharide. When such mutants are transformed to tetracycline resistance by plasmid pMC44, a hybrid plasmid that contains a 2 megadalton (Mdal) endonuclease EcoR1 fragment of E. coli K-12 DNA joined to the cloning vehicle-pSC101, capsular polysaccharide synthesis is inhibited and the transformed colonies exhibit a non-mucoid phenotype. Re-cloning of the 2 Mdal EcoR1 fragment onto plasmid pHA105, a min-colE1 plasmid, yielded plasmid pFM100 which also inhibited capsular polysaccharide synthesis in the capR mutants. A comparison of the polypeptides specified by both plasmids pFM100 and pMC44 in minicells demonstrated that seven polypeptide bands were specified by the 2 MDal DNA, one of which was previously demonstrated to be outer membrane protein a; also known as 3b or M2 (40 kilodaltons, Kdal). Plasmid mutants no longer repressing capsular polysaccharide synthesis were either unable to specify the 40 Kdal outer membrane protein a or were deficient in synthesis of 25 Kdal and 14.5 Kdal polypeptides specified by the 2 Mdal DNA fragments. Studies with a minicell-producing strain that also contained a capR mutation indicated that the capR gene product regulated processing of at least one normal protein, the precursor of outer membrane protein a.

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Bacterial ProteinsDNA, BacterialEscherichia coliMembrane ProteinsMutationOperonPhenotypePlasmidsPolysaccharides, BacterialTransformation, BacterialJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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R C Gayda, H Avni, P E Berg, A Markovitz. 1979-10-01. Outer membrane protein a and other polypeptides regulate capsular polysaccharide synthesis in E. coli K-12.. https://doi.org/10.1007/bf00397232

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