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A membrane-bound FtsH protease is invilved in osmoregulation in Synechocystis sp PCC 6803: the compatible solute synthesizing enzyme GgpS in one of the targets for proteolysis
Autor: Stirnberg, M; Fulda,S; Huckauf, J; Hagemann, M; Kramer, R; Marin,K
In:
Molecular Microbiology
Bandangabe: 63
Auflage: 1
ISBN: ISSN:0950-382x
Seite: 86 - 102
Jahr: 2007
Einordung:
Institut: Professur Agrobiotechnologie
Abstract:
Summary
Protein quality control and proteolysis are involved in
cell maintenance and environmental acclimatization
in bacteria and eukaryotes. The AAA protease FtsH2
of the cyanobacterium Synechocystis sp. PCC 6803
was identified during a screening for mutants
impaired in osmoregulation. The ftsH2– mutant was
salt sensitive because of a decreased level of the
osmoprotectant glucosylglycerol (GG). In spite of
wild type-like transcription of the ggpS gene in ftsH2–
cells the GgpS protein content increased but only low
levels of GgpS activity were observed. Consequently,
salt tolerance of the ftsH2– mutant decreased while
addition of external osmolyte complemented the salt
sensitivity. The proteolytic degradation of the GgpS
protein by FtsH2 was demonstrated by an in vitro
assay using inverted membrane vesicles. The GgpS
is part of a GG synthesizing complex, because yeast
two-hybrid screens identified a close interaction with
the GG-phosphate phosphatase. Besides GgpS as the
first soluble substrate of a cyanobacterial FtsH protease,
several other putative targets were identified
by a proteomic approach. We present a novel molecular
explanation for the salt-sensitive phenotype of
bacterial ftsH– mutants as the result of accumulation
of inactive enzymes for compatible solute synthesis,
in this case GgpS the key enzyme of GG synthesis. Ansprechpartner
Zur Publikation: Mitarbeiter,
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Letzte Änderung des Eintrages:
04.05.2010
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