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Structure. 2008 Jul;16(7):1095-104. doi: 10.1016/j.str.2008.03.020.

The tRNA-induced conformational activation of human mitochondrial phenylalanyl-tRNA synthetase.

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  • 1Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.

Abstract

All class II aminoacyl-tRNA synthetases (aaRSs) are known to be active as functional homodimers, homotetramers, or heterotetramers. However, multimeric organization is not a prerequisite for phenylalanylation activity, as monomeric mitochondrial phenylalanyl-tRNA synthetase (PheRS) is also active. We herein report the structure, at 2.2 A resolution, of a human monomeric mitPheRS complexed with Phe-AMP. The smallest known aaRS, which is, in fact, 1/5 of a cytoplasmic analog, is a chimera of the catalytic module of the alpha and anticodon binding domain (ABD) of the bacterial beta subunit of (alphabeta)2 PheRS. We demonstrate that the ABD located at the C terminus of mitPheRS overlaps with the acceptor stem of phenylalanine transfer RNA (tRNAPhe) if the substrate is positioned in a manner similar to that seen in the binary Thermus thermophilus complex. Thus, formation of the PheRS-tRNAPhe complex in human mitochondria must be accompanied by considerable rearrangement (hinge-type rotation through approximately 160 degrees) of the ABD upon tRNA binding.

PMID:
18611382
[PubMed - indexed for MEDLINE]
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