Open AccessOsmotic shock: A mechanosensitive channel blocker can prevent release of cytoplasmic but not periplasmic proteins
Author(s) -
Ewis Hosam E.,
Lu ChungDar
Publication year - 2005
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2005.09.046
Subject(s) - mechanosensitive channels , periplasmic space , osmotic shock , microbiology and biotechnology , cytoplasm , shock (circulatory) , chemistry , biophysics , biology , ion channel , biochemistry , medicine , escherichia coli , receptor , gene
When over‐expressed in the cytoplasm of Escherichia coli , carboxylesterase Est55 of Geobacillus stearothermophilus was found to be released from cells upon osmotic shock. Comparing two osmotic shock protocols showed that release of Est55 was abolished in the absence of mechanosensitive channel MscL by one method but not the other. The discrepancy extended to several previously reported cytoplasmic proteins released by osmotic shock, including: EF‐Tu, thioredoxin, and DnaK in E. coli . Stepwise analyses of parameters between these two protocols revealed that the use of mechanical pipetting instead of gentle dilution of cells prior to exposure to hypotonic solution abolished the effect of MscL. Furthermore, while this phenomenon of release of certain cytoplasmic proteins was sustained in all three wild type strains of E. coli , presence of gadolinium was able to serve as an MscL channel blocker and prevented release of Est55 and EF‐Tu in the process. An optimized protocol of osmotic shock was developed from this study to provide a more reliable assessment of location of proteins in E. coli . This method allowed release of authentic periplasmic MalE and β‐lactamase proteins comparable to that by EDTA‐lysozyme treatment.