Modulation of Aminoacylation and Editing Properties of Leucyl-tRNA Synthetase by a Conserved Structural Module.

ABSTRACT: A conserved structural module following the KMSKS catalytic loop exhibits ?-?-?-? topology in class Ia and Ib aminoacyl-tRNA synthetases. However, the function of this domain has received little attention. Here, we describe the effect this module has on the aminoacylation and editing capacities of leucyl-tRNA synthetases (LeuRSs) by characterizing the key residues from various species. Mutation of highly conserved basic residues on the third ?-helix of this domain impairs the affinity of LeuRS for the anticodon stem of tRNA(Leu), which decreases both aminoacylation and editing activities. Two glycine residues on this ?-helix contribute to flexibility, leucine activation, and editing of LeuRS from Escherichia coli (EcLeuRS). Acidic residues on the ?-strand enhance the editing activity of EcLeuRS and sense the size of the tRNA(Leu) D-loop. Incorporation of these residues stimulates the tRNA-dependent editing activity of the chimeric minimalist enzyme Mycoplasma mobile LeuRS fused to the connective polypeptide 1 editing domain and leucine-specific domain from EcLeuRS. Together, these results reveal the stem contact-fold to be a functional as well as a structural linker between the catalytic site and the tRNA binding domain. Sequence comparison of the EcLeuRS stem contact-fold domain with editing-deficient enzymes suggests that key residues of this module have evolved an adaptive strategy to follow the editing functions of LeuRS.

SUBMITTER: Yan W 

PROVIDER: S-EPMC4424357 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature