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Association of RNA with Thymidylate Synthase from Methotrexate-Resistant Streptococcus faecium
K. Narasimha Rao and Roy L. Kisliuk
Proceedings of the National Academy of Sciences of the United States of America
Vol. 80, No. 4, [Part 1: Biological Sciences] (Feb. 15, 1983), pp. 916-920
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/13853
Page Count: 5
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Thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 220.127.116.11) from methotrexate-resistant Streptococcus faecium has a UV absorbance peak at 259 nm and stains with acridine orange because of the presence of RNA on the protein. Material having an absorbance peak at 254 nm, obtained from the enzyme by phenol extraction, is degraded by treatment with pancreatic RNase, T1 RNase, and alkali but is stable to DNase. Dowex-1 chromatography of the pure enzyme yields two polynucleotide fragments in addition to the apoenzyme. As estimated from their absorbance, these fragments contain 4 and 11 mononucleotide residues per mole of enzyme, respectively. In crude extracts, thymidylate synthase is associated with rapidly sedimenting material that is sensitive to RNase. Treatment of crude extracts with RNase, as is done routinely during thymidylate synthase purification, most likely results in the formation of the small polynucleotides found on the enzyme. The RNA is not required for enzyme activity.
Proceedings of the National Academy of Sciences of the United States of America © 1983 National Academy of Sciences