Thermostable valyl-tRNA, isoleucyl-tRNA and methionyl-tRNA synthetases from an extreme thermophile Thermus thermophilus HB8: protein structure and Zn2+ binding |
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Authors: | D Kohda S Yokoyama T Miyazawa |
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Affiliation: | Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan |
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Abstract: | Thermostable valyl-tRNA, isoleucyl-tRNA and methionyl-tRNA synthetases have been purified from an extreme thermophile, Thermus thermophilus HB8. Valyl-tRNA and isoleucyl-tRNA synthetases are found to be monomer proteins (Mr 108000 and 129000, respectively), while methionyl-tRNA synthetase is a dimer protein (Mr 150000). These enzymes are very similar with respect to amino acid compositions and alpha-helix contents as estimated by circular dichroism analyses. Furthermore, two Zn2+ are tightly bound to each of these synthetases. These data suggest that valyl-tRNA and isoleucyl-tRNA synthetases consist of two domains, each corresponding to the subunit of methionyl-tRNA synthetase. |
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Keywords: | Valyl-tRNA synthetase Isoleucyl-tRNA synthetase Methionyl-tRNA synthetase Thermus thermophilus Amino acid composition Zinc content |
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