Expression of the divergent tricarboxylate transport operon (tctI) of Salmonella typhimurium.
AUTOR(ES)
Widenhorn, K A
RESUMO
Membrane-associated gene products of shock-sensitive bacterial transport operons are often difficult to detect. A 4.5-kilobase DNA fragment, known to completely encode the Salmonella typhimurium tctI operon, was cloned in both orientations behind the T7 phage promoter phi 10 and expressed by using the T7 polymerase-promoter system of Tabor and Richardson (S. Tabor and C. C. Richardson, Proc. Natl. Acad. Sci. USA 82:1074-1078, 1985). Under these conditions, five proteins were clearly demonstrated. One DNA strand was shown to encode the periplasmic (29,000-Mr) C protein (as a 31,000-Mr precursor), a 19,000-Mr protein, and a 40,000- to 45,000-Mr protein which ran as a diffuse band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The opposite strand carried the information for two additional proteins of 29,000 and 14,000 Mr. By Tn5 mutagenesis, subcloning of Tn5 insertions, and subcloning of various deletion mutants it was shown that the tctI system is divergently transcribed. The periplasmic binding protein (C protein) is the first product of one operon, followed by the 19,000-Mr and 45,000-Mr integral inner membrane proteins. On the opposite strand only the 29,000-Mr protein was essential for tctI function, and it was found to be weakly attached to the inner membrane. Thus tctI encodes four proteins, one periplasmic, two integral, and one peripheral to the cytoplasmic membrane, with the genes arranged as tctA tctB tctC tctD.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=211273Documentos Relacionados
- Genetic regulation of the tricarboxylate transport operon (tctI) of Salmonella typhimurium.
- Cloning and properties of the Salmonella typhimurium tricarboxylate transport operon in Escherichia coli.
- Fine-structure genetic map of the maltose transport operon of Salmonella typhimurium.
- Regulation of expression of the ilvB operon in Salmonella typhimurium.
- Electron microscopic visualization of trp operon expression in Salmonella typhimurium.