Evolutionary Basis of Converting a Bacterial tRNA Synthetase into a Yeast Cytoplasmic or Mitochondrial Enzyme

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Title:	Evolutionary Basis of Converting a Bacterial tRNA Synthetase into a Yeast Cytoplasmic or Mitochondrial Enzyme
Authors:	Chiu,WC;Chang,CP;Wang,CC
Contributors:	生命科學研究所
Keywords:	METHIONYL-TRANSFER-RNA;ELONGATION FACTOR-I;SACCHAROMYCES-CEREVISIAE;BINDING DOMAIN;MULTISYNTHETASE COMPLEX;RABBIT LIVER;GENE ENCODES;AMINOACYLATION;TRANSLATION;FEATURES
Date:	2009
Issue Date:	2010-06-29 19:28:57 (UTC+8)
Publisher:	中央大學
Abstract:	Previous studies showed that cytoplasmic and mitochondrial forms of yeast valyl-tRNA synthetase (ValRS) are specified by the VAS1 gene through alternative initiation of translation. Sequence comparison suggests that the yeast cytoplasmic (or mature mitochondrial) ValRS contains an N-terminal appendage that acts in cis as a nonspecific tRNA-binding domain (TRBD) and is absent from its bacterial relatives. We show here that Escherichia coli ValRS can substitute for the mitochondrial and cytoplasmic functions of VAS1 by fusion of a mitochondrial targeting signal and a TRBD, respectively. In addition, the bacterial ValRS gene can be converted into a dual functional yeast gene encoding both cytoplasmic and mitochondrial activities by fusion of a DNA sequence specifying both the mitochondrial targeting signal and TRBD. In vitro assays suggested that fusion of a nonspecific TRBD to the bacterial enzyme significantly enhanced its yeast tRNA-binding and aminoacylation activities. These results not only underscore the necessity of retaining a TRBD for functioning of a tRNA synthetase in yeast cytoplasm, but also provide insights into the evolution of tRNA synthetase genes.
Relation:	JOURNAL OF BIOLOGICAL CHEMISTRY
Appears in Collections:	[Graduate Institute of Life Science] journal & Dissertation

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