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J Bacteriol. 2000 Jan;182(1):143-5.

Cysteine biosynthesis pathway in the archaeon Methanosarcina barkeri encoded by acquired bacterial genes?

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  • 1Department of Molecular Biophysics and Biochemistry, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8114, USA.


The pathway of cysteine biosynthesis in archaea is still unexplored. Complementation of a cysteine auxotrophic Escherichia coli strain NK3 led to the isolation of the Methanosarcina barkeri cysK gene [encoding O-acetylserine (thiol)-lyase-A], which displays great similarity to bacterial cysK genes. Adjacent to cysK is an open reading frame orthologous to bacterial cysE (serine transacetylase) genes. These two genes could account for cysteine biosynthesis in this archaeon. Analysis of recent genome data revealed the presence of bacteria-like cysM genes [encoding O-acetylserine (thiol)-lyase-B] in Pyrococcus spp., Sulfolobus solfataricus, and Thermoplasma acidophilum. However, no orthologs for these genes can be found in Methanococcus jannaschii, Methanobacterium thermoautotrophicum, and Archaeoglobus fulgidus, implying the existence of unrecognizable genes for the same function or a different cysteine biosynthesis pathway.

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