Seryl-tRNA synthetase from Bombyx mori. Purification and properties |
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Authors: | S Viswanathan J D Dignam |
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Affiliation: | Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216-4505. |
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Abstract: | Seryl-tRNA synthetase has been purified from the middle silk glands of Bombyx mori by successive chromatography on DEAE-Sephacel, hydroxylapatite, and Bio-Rex 70. The high abundance of seryl-tRNA synthetase in the middle silk glands may result from an adaptation of this organ for the production of the serine-rich protein, sericin. The enzyme is a dimer of Mr = 124,000 consisting of similar or identical subunits and has an oligomeric structure similar to its procaryotic and eucaryotic counterparts. Seryl-tRNA synthetase can be cleaved with trypsin to generate a fragment of Mr = 45,000 on sodium dodecyl sulfate gels; the presence of tRNASer protects the enzyme from tryptic cleavage. Conversion to the Mr = 45,000 species is accompanied by a 90% loss in aminoacyl-tRNA synthetase activity, but only a 20% loss in ATP PPi exchange activity. |
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