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PDBsum entry 1e22
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Active site of lysyl-Trna synthetase: structural studies of the adenylation reaction.
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Authors
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G.Desogus,
F.Todone,
P.Brick,
S.Onesti.
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Ref.
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Biochemistry, 2000,
39,
8418-8425.
[DOI no: ]
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PubMed id
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Abstract
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Aminoacyl-tRNA synthetases play a key role in protein biosynthesis by catalyzing
the specific aminoacylation of tRNA. The energy required for the formation of
the ester bond between the amino acid carboxylate group and the tRNA acceptor
stem is supplied by coupling the reaction to the hydrolysis of ATP. Lysyl-tRNA
synthetase from Escherichia coli belongs to the family of class II synthetases
and carries out a two-step reaction, in which lysine is activated by being
attached to the alpha-phosphate of AMP before being transferred to the cognate
tRNA. Crystals of the thermo-inducible E. coli lysyl-tRNA synthetase LysU which
diffract to 2.1 A resolution have been used to determine crystal structures of
the enzyme in the presence of lysine, the lysyl-adenylate intermediate, and the
nonhydrolyzable ATP analogue AMP-PCP. Additional data have been obtained from
crystals soaked in a solution containing ATP and Mn(2+). The refined crystal
structures give "snapshots" of the active site corresponding to key steps in the
aminoacylation reaction and provide the structural framework for understanding
the mechanism of lysine activation. The active site of LysU is shaped to
position the substrates for the nucleophilic attack of the lysine carboxylate on
the ATP alpha-phosphate. No residues are directly involved in catalysis, but a
number of highly conserved amino acids and three metal ions coordinate the
substrates and stabilize the pentavalent transition state. A loop close to the
catalytic pocket, disordered in the lysine-bound structure, becomes ordered upon
adenine binding.
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