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Genetic analysis of selenocysteine biosynthesis in the archaeon Methanococcus maripaludis
Author(s) -
Hohn Michael J.,
Palioura Sotiria,
Su Dan,
Yuan Jing,
Söll Dieter
Publication year - 2011
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07690.x
Subject(s) - methanococcus , biology , transfer rna , selenocysteine , operon , gene , biochemistry , biosynthesis , sulfolobus solfataricus , mutant , genetics , archaea , enzyme , rna , cysteine
Summary In Archaea selenocysteine (Sec) is synthesized in three steps. First seryl‐tRNA synthetase acylates tRNA Sec with serine to generate Ser‐tRNA Sec . Then phosphoseryl‐tRNA Sec kinase (PSTK) forms Sep‐tRNA Sec , which is converted to Sec‐tRNA Sec by Sep‐tRNA:Sec‐tRNA synthase (SepSecS) in the presence of selenophosphate produced by selenophosphate synthetase (SelD). A complete in vivo analysis of the archaeal Sec biosynthesis pathway is still unavailable, and the existence of a redundant pathway or of a rescue mechanism based on the conversion of Sep‐tRNA Sec to Cys‐tRNA Sec during selenium starvation, cannot be excluded. Here we present a mutational analysis of Sec biosynthesis in Methanococcus maripaludis strain Mm900. Sec formation is abolished upon individually deleting the genes encoding SelD, PSTK or SepSecS; the resulting mutant strains could no longer grow on formate while growth with H 2 + CO 2 remained unaffected. However, deletion of the PSTK and SepSecS genes was not possible unless the selenium‐free [NiFe]‐hydrogenases Frc and Vhc were expressed. This required the prior deletion of either the gene encoding SelD or that of HrsM, a LysR‐type regulator suppressing transcription of the frc and vhc operons in the presence of selenium. These results show that M. maripaludis Mm900 is facultatively selenium‐dependent with a single pathway of Sec‐tRNA Sec formation.