Biochemical evidence for the secY24 defect in Escherichia coli protein translocation and its suppression by soluble cytoplasmic factors.
AUTOR(ES)
Fandl, J P
RESUMO
The secY (prlA) gene product is an integral membrane protein that has been identified genetically as one of the central components of the Escherichia coli protein translocation machinery. We have examined the effect of the secY24 (temperature-sensitive) mutation on the protein translocation activity of E. coli inverted membrane vesicles. Vesicles isolated from cells carrying this allele and grown at the nonpermissive temperature (42 degrees C) were less than 1% as active in translocation as vesicles isolated from an isogenic secY+ strain under the same conditions. Vesicles from the mutant strain grown at the permissive temperature (32 degrees C) were partially active, but those vesicles preincubated at 40 degrees C lost 90% of their activity. Moreover, the secY24 translocation defect on in vivo- or in vitro-inactivated vesicles was suppressed, or compensated, by an S300 soluble fraction from wild-type cells or from secY24 cells grown at nonpermissive temperature. The suppressing factor(s) was heat-labile and sensitive to proteinase K. These results provide biochemical evidence for the essential role of SecY in the translocation process and indicate that the translocation defect of SecY24 membranes can be compensated for by supplementing with additional soluble cytoplasmic proteins.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=299313Documentos Relacionados
- SecA suppresses the temperature-sensitive SecY24 defect in protein translocation in Escherichia coli membrane vesicles.
- Suppressors of the secY24 mutation: identification and characterization of additional ssy genes in Escherichia coli.
- Temperature-dependent insertion of prolipoprotein into Escherichia coli membrane vesicles and requirements for ATP, soluble factors, and functional SecY protein for the overall translocation process.
- SecF stabilizes SecD and SecY, components of the protein translocation machinery of the Escherichia coli cytoplasmic membrane.
- Roles of the C-Terminal End of SecY in Protein Translocation and Viability of Escherichia coli