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Outer membrane protein a and other polypeptides regulate capsular polysaccharide synthesis in E. coli K-12
Molecular & General Genetics : MGG
|October 1, 1979
Summary
Escherichia coli capR mutants overproduce capsular polysaccharide. Introducing specific plasmids inhibits this overproduction, revealing the capR gene product regulates outer membrane protein processing.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli K-12 capR mutants exhibit a mucoid phenotype due to excessive capsular polysaccharide production.
- Plasmid transformation can alter gene expression and cellular phenotypes in bacteria.
Purpose of the Study:
- To investigate the genetic basis of capsular polysaccharide synthesis regulation in Escherichia coli.
- To identify the specific gene products involved in the capR mutant phenotype.
Main Methods:
- Utilized plasmid transformation with engineered constructs (pMC44, pFM100) containing E. coli DNA fragments in capR mutants.
- Analyzed polypeptide synthesis in minicells to identify proteins encoded by the cloned DNA fragments.
- Studied minicell-producing strains with capR mutations to examine gene product regulation.
Main Results:
- Plasmids containing a 2 megadalton (Mdal) EcoR1 fragment of E. coli DNA inhibited capsular polysaccharide synthesis in capR mutants.
- The 2 Mdal DNA fragment encoded seven polypeptides, including outer membrane protein a (40 kilodaltons, Kdal).
- Mutations preventing repression of capsular polysaccharide synthesis were linked to the absence of outer membrane protein a or deficiencies in 25 Kdal and 14.5 Kdal polypeptides.
Conclusions:
- The capR gene product plays a regulatory role in processing at least one protein, specifically the precursor to outer membrane protein a.
- The identified DNA fragment and its encoded proteins are crucial for regulating capsular polysaccharide synthesis in Escherichia coli.