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B acillus subtilis spore protein SpoVAC functions as a mechanosensitive channel
Author(s) -
Velásquez Jeanette,
SchuurmanWolters Gea,
Birkner Jan Peter,
Abee Tjakko,
Poolman Bert
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12591
Subject(s) - mechanosensitive channels , vesicle , biology , biophysics , osmotic shock , spheroplast , osmotic concentration , dipicolinic acid , biochemistry , microbiology and biotechnology , membrane , spore , ion channel , escherichia coli , gene , receptor
Summary A critical event during spore germination is the release of Ca ‐ DPA (calcium in complex with dipicolinic acid). The mechanism of release of Ca ‐ DPA through the inner membrane of the spore is not clear, but proteins encoded by the B acillus subtilis spoVA operon are involved in the process. We cloned and expressed the spoVAC gene in E scherichia coli and characterized the SpoVAC protein. We show that SpoVAC protects E . coli against osmotic downshift, suggesting that it might act as a mechanosensitive channel. Purified SpoVAC was reconstituted in unilamellar lipid vesicles to determine the gating mechanism and pore properties of the protein. By means of a fluorescence‐dequenching assay, we show that SpoVAC is activated upon insertion into the membrane of the amphiphiles lyso PC and dodecylamine. Patch clamp experiments on E . coli giant spheroplast as well as giant unilamellar vesicles ( GUVs ) containing SpoVAC show that the protein forms transient pores with main conductance values of about 0.15 and 0.1 nS respectively. Overall, our data indicate that SpoVAC acts as a mechanosensitive channel and has properties that would allow the release of Ca ‐ DPA and amino acids during germination of the spore.