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Haloarchaea and the formation of gas vesicles.

Pfeifer F - Life (Basel) (2015)

Bottom Line: Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation.Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration.Except for GvpI and GvpH, all of these are required to form the gas permeable wall.

View Article: PubMed Central - PubMed

Affiliation: Microbiology and Archaea, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany. pfeifer@bio.tu-darmstadt.de.

ABSTRACT
Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation. Many Haloarchaea possess genes encoding gas vesicles, but only a few species, such as Halobacterium salinarum and Haloferax mediterranei, produce these gas-filled, proteinaceous nanocompartments. Gas vesicles increase the buoyancy of cells and enable them to migrate vertically in the water body to regions with optimal conditions. Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration. Fourteen gas vesicle protein (gvp) genes are involved in their formation, and regulation of gvp gene expression occurs at the level of transcription, including the two regulatory proteins, GvpD and GvpE, but also at the level of translation. The gas vesicle wall is solely formed of proteins with the two major components, GvpA and GvpC, and seven additional accessory proteins are also involved. Except for GvpI and GvpH, all of these are required to form the gas permeable wall. The applications of gas vesicles include their use as an antigen presenter for viral or pathogen proteins, but also as a stable ultrasonic reporter for biomedical purposes.

No MeSH data available.


Related in: MedlinePlus

Amino acid sequence of GvpA and the structure derived from the in silico modelling. (a) Amino acid sequence of pGvpA and the proposed 2D structure (model). H denotes α-helices and E β-strands. The α-helices, H1 and H2, and the anti-parallel β-strands are indicated on top. (b) Electron micrograph of a Vac− ∆A + Amut transformant, showing that gas-filled compartments are indeed lacking in such mutants. (c) Structure of GvpA, highlighting some positions of ala-substitutions leading to gas vesicle negative ∆A + Amut transformants [63]. The respective single amino acids that are altered are shown in bold in (a).
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life-05-00385-f005: Amino acid sequence of GvpA and the structure derived from the in silico modelling. (a) Amino acid sequence of pGvpA and the proposed 2D structure (model). H denotes α-helices and E β-strands. The α-helices, H1 and H2, and the anti-parallel β-strands are indicated on top. (b) Electron micrograph of a Vac− ∆A + Amut transformant, showing that gas-filled compartments are indeed lacking in such mutants. (c) Structure of GvpA, highlighting some positions of ala-substitutions leading to gas vesicle negative ∆A + Amut transformants [63]. The respective single amino acids that are altered are shown in bold in (a).

Mentions: GvpA constitutes the almost crystalline gas vesicle wall, forming a helix of low pitch seen as ribs running perpendicular to the long axis by transmission electron microscopy [58,59]. The gas vesicle wall is difficult to disaggregate, and the protein constituents are difficult to analyze. Immunological methods and MALDI-TOF mass spectrometry indicate that with the exception of GvpK, all Gvp proteins are present [60,61]. The sequence of the 8-kDa GvpA is highly conserved between archaeal and also bacterial gas vesicle producers (see Figure 4), and differences occur mainly near the N- and C-terminus. GvpA is not post-translationally modified, as demonstrated by protein sequencing and MALDI-TOF mass spectrometry [59,61]. A crystal structure of GvpA is not available due to its hydrophobic nature and high tendency to aggregate. The secondary structure prediction of GvpA suggests a coil-α-β-β-α-coil fold (Figure 5a) [62,63]. Solid-state NMR and Fourier transform infrared spectroscopy (FTIR) with isolated gas vesicles indicates anti-parallel β-sheets, and X-ray analyses and atomic force microscopy imply that the β-strands of GvpA are tilted in the ribs at an angle of 54° [59,62,64]. The C-terminal portion of GvpA is exposed to the outside of the gas vesicles, since a trypsin site and several endopeptidase GluC sites are accessible here, whereas other portions of GvpA are protected [61].


Haloarchaea and the formation of gas vesicles.

Pfeifer F - Life (Basel) (2015)

Amino acid sequence of GvpA and the structure derived from the in silico modelling. (a) Amino acid sequence of pGvpA and the proposed 2D structure (model). H denotes α-helices and E β-strands. The α-helices, H1 and H2, and the anti-parallel β-strands are indicated on top. (b) Electron micrograph of a Vac− ∆A + Amut transformant, showing that gas-filled compartments are indeed lacking in such mutants. (c) Structure of GvpA, highlighting some positions of ala-substitutions leading to gas vesicle negative ∆A + Amut transformants [63]. The respective single amino acids that are altered are shown in bold in (a).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390858&req=5

life-05-00385-f005: Amino acid sequence of GvpA and the structure derived from the in silico modelling. (a) Amino acid sequence of pGvpA and the proposed 2D structure (model). H denotes α-helices and E β-strands. The α-helices, H1 and H2, and the anti-parallel β-strands are indicated on top. (b) Electron micrograph of a Vac− ∆A + Amut transformant, showing that gas-filled compartments are indeed lacking in such mutants. (c) Structure of GvpA, highlighting some positions of ala-substitutions leading to gas vesicle negative ∆A + Amut transformants [63]. The respective single amino acids that are altered are shown in bold in (a).
Mentions: GvpA constitutes the almost crystalline gas vesicle wall, forming a helix of low pitch seen as ribs running perpendicular to the long axis by transmission electron microscopy [58,59]. The gas vesicle wall is difficult to disaggregate, and the protein constituents are difficult to analyze. Immunological methods and MALDI-TOF mass spectrometry indicate that with the exception of GvpK, all Gvp proteins are present [60,61]. The sequence of the 8-kDa GvpA is highly conserved between archaeal and also bacterial gas vesicle producers (see Figure 4), and differences occur mainly near the N- and C-terminus. GvpA is not post-translationally modified, as demonstrated by protein sequencing and MALDI-TOF mass spectrometry [59,61]. A crystal structure of GvpA is not available due to its hydrophobic nature and high tendency to aggregate. The secondary structure prediction of GvpA suggests a coil-α-β-β-α-coil fold (Figure 5a) [62,63]. Solid-state NMR and Fourier transform infrared spectroscopy (FTIR) with isolated gas vesicles indicates anti-parallel β-sheets, and X-ray analyses and atomic force microscopy imply that the β-strands of GvpA are tilted in the ribs at an angle of 54° [59,62,64]. The C-terminal portion of GvpA is exposed to the outside of the gas vesicles, since a trypsin site and several endopeptidase GluC sites are accessible here, whereas other portions of GvpA are protected [61].

Bottom Line: Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation.Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration.Except for GvpI and GvpH, all of these are required to form the gas permeable wall.

View Article: PubMed Central - PubMed

Affiliation: Microbiology and Archaea, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany. pfeifer@bio.tu-darmstadt.de.

ABSTRACT
Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation. Many Haloarchaea possess genes encoding gas vesicles, but only a few species, such as Halobacterium salinarum and Haloferax mediterranei, produce these gas-filled, proteinaceous nanocompartments. Gas vesicles increase the buoyancy of cells and enable them to migrate vertically in the water body to regions with optimal conditions. Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration. Fourteen gas vesicle protein (gvp) genes are involved in their formation, and regulation of gvp gene expression occurs at the level of transcription, including the two regulatory proteins, GvpD and GvpE, but also at the level of translation. The gas vesicle wall is solely formed of proteins with the two major components, GvpA and GvpC, and seven additional accessory proteins are also involved. Except for GvpI and GvpH, all of these are required to form the gas permeable wall. The applications of gas vesicles include their use as an antigen presenter for viral or pathogen proteins, but also as a stable ultrasonic reporter for biomedical purposes.

No MeSH data available.


Related in: MedlinePlus