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Disruption and complementation of the selenocysteine biosynthesis pathway reveals a hierarchy of selenoprotein gene expression in the archaeon Methanococcus maripaludis
Author(s) -
Stock Tilmann,
Selzer Mirjam,
Connery Sarah,
Seyhan Deniz,
Resch Armin,
Rother Michael
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.1365-2958.2011.07850.x
Subject(s) - selenocysteine , methanococcus , biology , complementation , selenoprotein , transfer rna , biochemistry , genetics , gene , mutant , escherichia coli , rna , enzyme , cysteine , glutathione , glutathione peroxidase
Summary Proteins containing selenocysteine are found in members of all three domains of life, Bacteria, Eukarya and Archaea. A dedicated tRNA (tRNA sec ) serves as a scaffold for selenocysteine synthesis. However, sequence and secondary structures differ in tRNA sec from the different domains. An Escherichia coli strain lacking the gene for tRNA sec could only be complemented with the homologue from Methanococcus maripaludis when a single base in the anticodon loop was exchanged demonstrating that this base is a crucial determinant for archaeal tRNA sec to function in E. coli . Complementation in trans of M. maripaludis JJ mutants lacking tRNA sec , O ‐phosphoseryl‐tRNA sec kinase or O ‐phosphoseryl‐tRNA sec :selenocysteine synthase with the corresponding genes from M. maripaludis S2 restored the mutant's ability to synthesize selenoproteins. However, only partial restoration of the wild‐type selenoproteome was observed as only selenocysteine‐containing formate dehydrogenase was synthesized. Quantification of transcripts showed that disrupting the pathway of selenocysteine synthesis leads to downregulation of selenoprotein gene expression, concomitant with upregulation of a selenium‐independent backup system, which is not re‐adjusted upon complementation. This transcriptional arrest was independent of selenophosphate but depended on the ‘history’ of the mutants and was inheritable, which suggests that a stable genetic switch may cause the resulting hierarchy of selenoproteins synthesized.