A tRNA-dependent cysteine biosynthesis enzyme recognizes the selenocysteine-specific tRNA in Escherichia coli |
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| Authors: | Jing Yuan R Lynn Sherrer Dan Su |
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| Institution: | a Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
b Department of Chemistry, Yale University, New Haven, CT 06520-8114, USA |
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| Abstract: | The essential methanogen enzyme Sep-tRNA:Cys-tRNA synthase (SepCysS) converts O-phosphoseryl-tRNACys (Sep-tRNACys) into Cys-tRNACys in the presence of a sulfur donor. Likewise, Sep-tRNA:Sec-tRNA synthase converts O-phosphoseryl-tRNASec (Sep-tRNASec) to selenocysteinyl-tRNASec (Sec-tRNASec) using a selenium donor. While the Sep moiety of the aminoacyl-tRNA substrates is the same in both reactions, tRNACys and tRNASec differ greatly in sequence and structure. In an Escherichia coli genetic approach that tests for formate dehydrogenase activity in the absence of selenium donor we show that Sep-tRNASec is a substrate for SepCysS. Since Sec and Cys are the only active site amino acids known to sustain FDH activity, we conclude that SepCysS converts Sep-tRNASec to Cys-tRNASec, and that Sep is crucial for SepCysS recognition. |
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| Keywords: | aa-tRNA aminoacyl-tRNA EF-Tu elongation factor Tu FDHH formate dehydrogenase H FDHN formate dehydrogenase N IPTG d-thiogalactoside" target="_blank">isopropyl-d-thiogalactoside PLP pyridoxal phosphate PSTK phosphoseryl-tRNASec kinase Sec selenocysteine SelA selenocysteine synthase SelB elongation factor SelB SelD selenophosphate synthetase Sep O-phosphoserine SepCysS Sep-tRNA:Cys-tRNA synthase SepSecS Sep-tRNA:Sec-tRNA synthase |
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