title: Bacillus subtilis spore protein SpoVAC functions as a mechanosensitive channel.
abstract: 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 Bacillus subtilis spoVA operon are involved in the process. We cloned and expressed the spoVAC gene in Escherichia 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 lysoPC 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.
authors.affiliation: Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands; TI Food and Nutrition, Wageningen, The Netherlands.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Velásquez
authors.forename: Gea
authors.initials: G
authors.lastname: Schuurman-Wolters
authors.forename: Jan Peter
authors.initials: JP
authors.lastname: Birkner
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
authors.forename: Bert
authors.initials: B
authors.lastname: Poolman
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D015640:Ion Channel Gating; D055595:Mechanical Phenomena; D008565:Membrane Proteins / Q000378:metabolism*; D013171:Spores, Bacterial / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins