title: Functional studies of the gvpACNO operon of Halobacterium salinarium reveal that the GvpC protein shapes gas vesicles.
abstract: Gas vesicle (Vac) synthesis in Halobacterium salinarium PHH1 involves the expression of the plasmid pHH1-encoded vac (p-vac) region consisting of 14 different gvp genes that are arranged in two clusters, p-gvpACNO and, oriented in the direction opposite to that of gvpA, p-gvpDEFGHIJKLM. The p-gvpACNO region was analyzed at the transcriptional and functional levels in H. salinarium and in Haloferax volcanii transformants containing subfragments of the p-vac region. The p-gvpACNO genes were transcribed as several mRNAs: the 270-nucleotide (nt) p-gvpA transcript, encoding the major structural protein, occurred in large amounts, and minor amounts of three different readthrough transcripts (p-gvpACN, and p-gvpACNO mRNA) were found. In addition, the p-gvpO gene gave rise to two separate mRNA species: a 550-nt mRNA starting at the ATG and spanning the entire reading frame and a 420-nt RNA encompassing the second half of the p-gvpO gene. The requirement of p-gvpC, p-gvpN, and p-gvpO gene expression for gas vesicle synthesis was assessed by transformation experiments using the VAC- species Haloferax volcanii as the recipient. A delta C transformant, harboring the p-vac region with a deletion of the p-gvpC gene, produced large amounts of irregularly shaped gas vesicles. A shape-forming function of p-GvpC was demonstrated by complementation of the delta C transformant with the p-gvpC gene, resulting in wild-type-shaped gas vesicles. In the delta N transformant, the level of gas vesicle synthesis was very low, indicating that the p-GvpN protein is not required for gas vesicle assembly but may enhance gas vesicle synthesis. The p-gvpN deletion did not affect accumulation of p-gvpACO mRNA but reduced the separate p-gvpO transcription. The delta O transformant was Vac- and had a strongly decreased level of p-gvpACN mRNAs, demonstrating that the p-GvpO protein is required for gas vesicle synthesis and may affect transcription of this DNA region.
authors.affiliation: Institut für Mikrobiologie und Genetik, Technische Hochschule Darmstadt, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Offner
authors.forename: G
authors.initials: G
authors.lastname: Wanner
authors.forename: F
authors.initials: F
authors.lastname: Pfeifer
mesh_terms: D019843:Archaeal Proteins; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D015152:Blotting, Northern; D004269:DNA, Bacterial; D006216:Halobacteriaceae / Q000235:genetics; D006217:Halobacterium / Q000235:genetics* / Q000648:ultrastructure; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D009876:Operon; D010641:Phenotype; D011506:Proteins; D012333:RNA, Messenger / Q000235:genetics; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014169:Transformation, Bacterial
chemical_list: D019843:Archaeal Proteins; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; D011506:Proteins; D012333:RNA, Messenger; C038524:gas vesicle protein