One polypeptide with two aminoacyl-tRNA synthetase activities |
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Authors: | Stathopoulos C Li T Longman R Vothknecht U C Becker H D Ibba M Söll D |
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Institution: | Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA. |
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Abstract: | The genome sequences of certain archaea do not contain recognizable cysteinyl-transfer RNA (tRNA) synthetases, which are essential for messenger RNA-encoded protein synthesis. However, a single cysteinyl-tRNA synthetase activity was detected and purified from one such organism, Methanococcus jannaschii. The amino-terminal sequence of this protein corresponded to the predicted sequence of prolyl-tRNA synthetase. Biochemical and genetic analyses indicated that this archaeal form of prolyl-tRNA synthetase can synthesize both cysteinyl-tRNA(Cys) and prolyl-tRNA(Pro). The ability of one enzyme to provide two aminoacyl-tRNAs for protein synthesis raises questions about concepts of substrate specificity in protein synthesis and may provide insights into the evolutionary origins of this process. |
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