engleski

Adaptation of Aminoacyl-tRNA Synthetase Catalytic Core to Carrier Protein Aminoacylation

Amino acid:[carrier protein] ligases (aa:CP ligases) are newly discovered enzymes that are highly similar to class II aminoacyl-tRNA synthetases (aaRSs). However, while aaRSs aminoacylate tRNA and supply building blocks for ribosomal translation, aa:CP ligases transfer activated amino acids to the phosphopantetheine group of small carrier proteins. We have solved the crystal structure of an aa:CP ligase complexed with the carrier protein (CP). The CP prosthetic group enters the active site from a different direction than tRNA in class II aaRS complexes, through an idiosyncratic tunnel. CP binds to aa:CP ligase in fundamentally different manner compared to tRNA binding by structurally closely related aaRSs. Based on crystallographic analysis, an enzyme of altered CP specificity was designed, and the mechanism of amino acid transfer to the prosthetic group was proposed. The presented study reveals how conserved class II aaRS catalytic core can adapt to a novel function through minor structural alterations.

aaRS homologs ; amino acid:[carrier protein] ligase ; carrier protein ; noncanonical functions of aaRS ; seryl-tRNA synthetase

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