SecD and SecF facilitate protein export in Escherichia coli.
AUTOR(ES)
Pogliano, J A
RESUMO
We show here that the rate of protein translocation in the bacterium Escherichia coli depends on the levels of the SecD and SecF proteins in the cell. Overexpression of SecD and SecF stimulates translocation in wild type cells and improves export of proteins with mutant signal sequences. Depletion of SecD and SecF from the cell greatly reduces but does not abolish protein translocation. A secDF::kan null mutant deleted for the genes encoding both proteins is cold-sensitive for growth and protein export, has a severe export defect at 37 degrees C and is barely viable. The phenotypes of a secD null mutant and a secF null mutant are identical to the secDF::kan double null mutant. These results partially resolve the conflict between genetic studies and results from in vitro translocation systems which do not require SecD and SecF for activity, affirm the importance of these proteins to the export process, and suggest that SecD and SecF function together to stimulate protein export in a role fundamentally different from other Sec proteins. Our results provide additional support for the notion that an early step in protein export is cold-sensitive.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=394844Documentos Relacionados
- Export of the outer membrane lipoprotein is defective in secD, secE, and secF mutants of Escherichia coli.
- SecF stabilizes SecD and SecY, components of the protein translocation machinery of the Escherichia coli cytoplasmic membrane.
- secD, a new gene involved in protein export in Escherichia coli.
- SecD and SecF are required for the proton electrochemical gradient stimulation of preprotein translocation.
- The secD locus of E. coli codes for two membrane proteins required for protein export.