1f4l: Difference between revisions

[[Image:1f4l.jpg|left|200px]]<br /><applet load="1f4l" size="350" color="white" frame="true" align="right" spinBox="true"  

Amino acid selection by aminoacyl-tRNA synthetases requires efficient mechanisms to avoid incorrect charging of the cognate tRNAs. A proofreading mechanism prevents Escherichia coli methionyl-tRNA synthetase (EcMet-RS) from activating in vivo L-homocysteine, a natural competitor of L-methionine recognised by the enzyme. The crystal structure of the complex between EcMet-RS and L-methionine solved at 1.8 A resolution exhibits some conspicuous differences with the recently published free enzyme structure. Thus, the methionine delta-sulphur atom replaces a water molecule H-bonded to Leu13N and Tyr260O(eta) in the free enzyme. Rearrangements of aromatic residues enable the protein to form a hydrophobic pocket around the ligand side-chain. The subsequent formation of an extended water molecule network contributes to relative displacements, up to 3 A, of several domains of the protein. The structure of this complex supports a plausible mechanism for the selection of L-methionine versus L-homocysteine and suggests the possibility of information transfer between the different functional domains of the enzyme.

1F4L is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=ZN:'>ZN</scene> and <scene name='pdbligand=MET:'>MET</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Methionine--tRNA_ligase Methionine--tRNA ligase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.1.1.10 6.1.1.10] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1F4L OCA].  

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