title: Lactococcus lactis uses MscL as its principal mechanosensitive channel.
abstract: The functions of the mechanosensitive channels from Lactococcus lactis were determined by biochemical, physiological, and electrophysiological methods. Patch-clamp studies showed that the genes yncB and mscL encode MscS and MscL-like channels, respectively, when expressed in Escherichia coli or if the gene products were purified and reconstituted in proteoliposomes. However, unless yncB was expressed in trans, wild type membranes of L. lactis displayed only MscL activity. Membranes prepared from an mscL disruption mutant did not show any mechanosensitive channel activity, irrespective of whether the cells had been grown on low or high osmolarity medium. In osmotic downshift assays, wild type cells survived and retained 20% of the glycine betaine internalized under external high salt conditions. On the other hand, the mscL disruption mutant retained 40% of internalized glycine betaine and was significantly compromised in its survival upon osmotic downshifts. The data strongly suggest that L. lactis uses MscL as the main mechanosensitive solute release system to protect the cells under conditions of osmotic downshift.
authors.affiliation: Department of Biochemistry, Groninger Biomolecular Sciences and Biotechnology Institute and Material Science Centreplus, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
authors.forename: Joost H A
authors.initials: JH
authors.lastname: Folgering
authors.forename: Paul C
authors.initials: PC
authors.lastname: Moe
authors.forename: Gea K
authors.initials: GK
authors.lastname: Schuurman-Wolters
authors.forename: Paul
authors.initials: P
authors.lastname: Blount
authors.forename: Bert
authors.initials: B
authors.lastname: Poolman
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D003553:Cystine; D017931:DNA Primers; D015964:Gene Expression Regulation, Bacterial; D013294:Lactococcus lactis / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D020346:Aquaporins; D015220:Calcium Channels; D017931:DNA Primers; D003553:Cystine