2aev
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(New page: 200px<br /><applet load="2aev" size="450" color="white" frame="true" align="right" spinBox="true" caption="2aev, resolution 2.00Å" /> '''MJ0158, NaBH4-reduce...)
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Revision as of 05:58, 21 November 2007
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MJ0158, NaBH4-reduced form
Overview
Bacterial selenocysteine synthase converts seryl-tRNA(Sec) to, selenocysteinyl-tRNA(Sec) for selenoprotein biosynthesis. The identity of, this enzyme in archaea and eukaryotes is unknown. On the basis of sequence, similarity, a conserved open reading frame has been annotated as a, selenocysteine synthase gene in archaeal genomes. We have determined the, crystal structure of the corresponding protein from Methanococcus, jannaschii, MJ0158. The protein was found to be dimeric with a distinctive, domain arrangement and an exposed active site, built from residues of the, large domain of one protomer alone. The shape of the dimer is reminiscent, of a substructure of the decameric Escherichia coli selenocysteine, synthase seen in electron microscopic projections. However, biochemical, analyses demonstrated that MJ0158 lacked affinity for E. coli, seryl-tRNA(Sec) or M. jannaschii seryl-tRNA(Sec), and neither substrate, was directly converted to selenocysteinyl-tRNA(Sec) by MJ0158 when, supplied with selenophosphate. We then tested a hypothetical M. jannaschii, O-phosphoseryl-tRNA(Sec) kinase and demonstrated that the enzyme converts, seryl-tRNA(Sec) to O-phosphoseryl-tRNA(Sec) that could constitute an, activated intermediate for selenocysteinyl-tRNA(Sec) production. MJ0158, also failed to convert O-phosphoseryl-tRNA(Sec) to, selenocysteinyl-tRNA(Sec). In contrast, both archaeal and bacterial, seryl-tRNA synthetases were able to charge both archaeal and bacterial, tRNA(Sec) with serine, and E. coli selenocysteine synthase converted both, types of seryl-tRNA(Sec) to selenocysteinyl-tRNA(Sec). These findings, demonstrate that a number of factors from the selenoprotein biosynthesis, machineries are cross-reactive between the bacterial and the archaeal, systems but that MJ0158 either does not encode a selenocysteine synthase, or requires additional factors for activity.
About this Structure
2AEV is a Single protein structure of sequence from Methanocaldococcus jannaschii with SO4 as ligand. Full crystallographic information is available from OCA.
Reference
Structural and functional investigation of a putative archaeal selenocysteine synthase., Kaiser JT, Gromadski K, Rother M, Engelhardt H, Rodnina MV, Wahl MC, Biochemistry. 2005 Oct 11;44(40):13315-27. PMID:16201757
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