Structural insights into the first step of RNA-dependent cysteine biosynthesis in archaea

Nat Struct Mol Biol. 2007 Apr;14(4):272-9. doi: 10.1038/nsmb1219. Epub 2007 Mar 11.

Abstract

Cysteine is ligated to tRNA(Cys) by cysteinyl-tRNA synthetase in most organisms. However, in methanogenic archaea lacking cysteinyl-tRNA synthetase, O-phosphoserine is ligated to tRNA(Cys) by O-phosphoseryl-tRNA synthetase (SepRS), and the phosphoseryl-tRNA(Cys) is converted to cysteinyl-tRNA(Cys). In this study, we determined the crystal structure of the SepRS tetramer in complex with tRNA(Cys) and O-phosphoserine at 2.6-A resolution. The catalytic domain of SepRS recognizes the negatively charged side chain of O-phosphoserine at a noncanonical site, using the dipole moment of a conserved alpha-helix. The unique C-terminal domain specifically recognizes the anticodon GCA of tRNA(Cys). On the basis of the structure, we engineered SepRS to recognize tRNA(Cys) mutants with the anticodons UCA and CUA and clarified the anticodon recognition mechanism by crystallography. The mutant SepRS-tRNA pairs may be useful for translational incorporation of O-phosphoserine into proteins in response to the stop codons UGA and UAG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Anticodon / genetics
  • Archaeal Proteins / chemistry*
  • Archaeal Proteins / metabolism*
  • Archaeoglobus fulgidus / enzymology*
  • Biological Evolution
  • Crystallography, X-Ray
  • Cysteine / biosynthesis*
  • Models, Molecular
  • Molecular Sequence Data
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Phosphoserine / metabolism
  • Protein Engineering
  • Protein Structure, Secondary
  • RNA, Archaeal / metabolism*
  • RNA, Transfer, Cys / metabolism

Substances

  • Anticodon
  • Archaeal Proteins
  • Mutant Proteins
  • RNA, Archaeal
  • RNA, Transfer, Cys
  • Phosphoserine
  • Cysteine

Associated data

  • PDB/2DU3
  • PDB/2DU4
  • PDB/2DU5
  • PDB/2DU6
  • PDB/2DU7