title: Structural characteristics of halobacterial gas vesicles.
abstract: Gas vesicle formation in halophilic archaea is encoded by a DNA region (the vac region) containing 14 different genes: gvpACNO and gvpDEFGHIJKLM. In Halobacterium salinarum PHH1 (which expresses the p-vac region from plasmid pHH1), gas vesicles are spindle shaped, whereas predominantly cylindrical gas vesicles are synthesized by the chromosomal c-vac region of H. salinarum PHH4 and the single chromosomal mc-vac region of Haloferax mediterranei. Homologous complementation of gvp gene clusters derived from the chromosomal c-vac region led to cylindrical gas vesicles in transformants and proved that the activity of the c-gvpA promoter depended on a gene product from the c-gvpE-M DNA region. Heterologous complementation experiments with transcription units of different vac regions demonstrated that the formation of chimeric gas vesicles was possible. Comparison of micrographs of wild-type and chimeric gas vesicles indicated that the shape was not exclusively determined by GvpA, the major structural protein of the gas vesicle wall. More likely, a dynamic equilibrium of several gvp gene products was responsible for determination of the shape. Transmission electron microscopy of frozen hydrated, wild-type gas vesicles showed moiré patterns due to the superposition of the front and back parts of the ribbed gas vesicle envelope. Comparison of projections of model helices with the moiré pattern seen on the cylindrical part of the gas vesicles provided evidence that the ribs formed a helix of low pitch and not a stack of hoops.
authors.affiliation: Institut für Mikrobiologie und Genetik, Technische Universität Darmstadt, Schnittspahnstr. 10, D-64287 Darmstadt, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Offner
authors.affiliation: Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Ziese
authors.affiliation: Institut für Botanik, Ludwig-Maximilians-Universität München, D-80992 München, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wanner
authors.affiliation: Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Typke
authors.affiliation: Institut für Mikrobiologie und Genetik, Technische Universität Darmstadt, Schnittspahnstr. 10, D-64287 Darmstadt, Germany.
authors.forename: Felicitas
authors.initials: F
authors.lastname: Pfeifer
mesh_terms: D019843:Archaeal Proteins / Q000378:metabolism; D019641:DNA, Archaeal; D019848:Gene Expression Regulation, Archaeal; D019766:Genes, Archaeal; D005816:Genetic Complementation Test; D006217:Halobacterium / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*; D019621:Haloferax / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D014170:Transformation, Genetic; D014617:Vacuoles / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D019843:Archaeal Proteins; D019641:DNA, Archaeal