Die Demethylierung von Dimethylselenid ist eine adaptive Antwort des Archaeons Methanococcus voltae
Loading...
Files
Date
Authors
Publisher
Philipps-Universität Marburg
Supervisors
Abstract
Selenium is a trace element which is important
for many organisms. It is a constituent of proteins, where it
is found as selenocysteine or selenomethionine, and of special
nucleotides of tRNA bases. High concentrations of selenium are
toxic for most organisms. Detoxification can be achieved by
volatilization through methylation. Different methylation
products have been found. The most abundant one is
dimethylselenide which can probably be generated in different
ways from inorganic selenium compounds. Dimethylselenide
production is performed by microorganisms and plants and has
been monitored in soil and marine environments. Although
selenium is widely distributed in the environment, it is not
always readily available. While inorganic selenium compounds,
such as selenite and selenate are soluble, selenides can be
very insoluble as is elementary selenium which can be formed
from the oxidized species. Selenium can thus become limiting in
anoxic environments. Access to selenium is essential for
organisms depending on selenium-containing enzymes in their
central metabolism. This is the case for at least two known
methanogenic archaea Methanocaldococcus jannaschii and
Methanococcus voltae. Both organisms convert hydrogen and
carbon dioxide to methane, whereby the cells generate their
energy. Two selenium containing hydrogenases, enzymes needed to
oxidize hydrogen for the generation of electrons, are involved
in the methanogenic pathway. Limiting selenium in growth media
for M. voltae leads to a reduced growth rate and the knockout
of a gene encoding a selenium-containing subunit of a
hydrogenase has not been possible. While limited growth of M.
voltae has been observed under selenium depletion, M.
jannaschii cannot grow without selenium. It was previously
shown that M. voltae carries genes encoding selenium-free
isoenzymes of its selenium-containing hydrogenases which are
only transcribed upon selenium limitation and most likely
supplement the selenium enzymes. The cell can thus react to the
deprivation of the trace element. We were interested in
learning more about functions of proteins produced only under
selenium limitation. The protein patterns in extracts obtained
from of M. voltae cells grown with or without selenium were
therefore analyzed. Subsequently, a protein that was induced by
selenium deprivation was further characterized. This putative
corrinoid protein together with a methyltransferase is involved
in the liberation of selenium from the organic selenium
compound dimethylselenide. The two respective genes are part of
a common transcription unit. Their regulation occurs at the
level of transcription or by regulation of transcript
stability. This inducible demethylation of dimethylselenide
constitutes a novel, alternative adaptation strategy of M.
voltae to selenium limitation.
Review
Metadata
Contributors
Supervisor:
Dates
Created: 2004Issued: 2004-05-19Updated: 2011-08-10
Faculty
Fachbereich Biologie
Publisher
Philipps-Universität Marburg
Language
ger
Data types
DoctoralThesis
Keywords
Dimethylselenide , MethyltransferasesArchaeaMethanococcus , Selenium
DFG-subjects
DimethylselenidMethanococcusArchaeaMethyltransferasenSelen
DDC-Numbers
570
show more
Niess, Ulf Michael: Die Demethylierung von Dimethylselenid ist eine adaptive Antwort des Archaeons Methanococcus voltae. : Philipps-Universität Marburg 2004-05-19. DOI: https://doi.org/10.17192/z2004.0131.
License
This item has been published with the following license: In Copyright