Toward Understanding Phosphoseryl-tRNA Cys Formation: The Crystal Structure of Methanococcus maripaludis Phosphoseryl-tRNA Synthetase
A number of archaeal organisms generate Cys-tRNA{sup Cys} in a two-step pathway, first charging phosphoserine (Sep) onto tRNA{sup Cys} and subsequently converting it to Cys-tRNA{sup Cys}. We have determined, at 3.2-{angstrom} resolution, the structure of the Methanococcus maripaludis phosphoseryl-tRNA synthetase (SepRS), which catalyzes the first step of this pathway. The structure shows that SepRS is a class II, {alpha}{sub 4} synthetase whose quaternary structure arrangement of subunits closely resembles that of the heterotetrameric ({alpha}{beta}){sub 2} phenylalanyl-tRNA synthetase (PheRS). Homology modeling of a tRNA complex indicates that, in contrast to PheRS, a single monomer in the SepRS tetramer may recognize both the acceptor terminus and anticodon of a tRNA substrate. Using a complex with tungstate as a marker for the position of the phosphate moiety of Sep, we suggest that SepRS and PheRS bind their respective amino acid substrates in dissimilar orientations by using different residues.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 930394
- Report Number(s):
- BNL-81116-2008-JA; PNASA6; TRN: US200904%%674
- Journal Information:
- Proceedings of the National Academy of Sciences of the USA, Vol. 104, Issue 8; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- English
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