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Purification and characterization of transfer RNA (guanine-1)methyltransferase from Escherichia coli.
Umeå University, Faculty of Medicine, Molecular Biology.
Umeå University, Faculty of Medicine, Molecular Biology. Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
1983 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 258, no 2, 1343-1351 p.Article in journal (Refereed) Published
Abstract [en]

The tRNA modifying enzyme, tRNA (guanine-1)methyltransferase has been purified to near homogeneity from an overproducing Escherichia coli strain harboring a multicopy plasmid carrying the structural gene of the enzyme. The preparation gives a single major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is probably a single polypeptide chain of molecular weight 32,000. The amino acid composition is presented and the NH2-terminal amino acid sequence was established to be H2N-Met-Trp-Ile-Gly-Ile-Ile-Ser-Leu-Phe-Pro. The enzyme has a pI of 5.2. The tRNA (guanine-1)-methyltransferase has a pH optimum of 8.0-8.5, an apparent Km of 5 microM for S-adenosylmethionine. S-adenosylhomocysteine is a competitive inhibitor for the enzyme with an apparent Ki of 6 microM. Spermidine or putrescine are not required for activity, but they stimulate the rate of methylation 1.2-fold with optima at 2 and 6 mM, respectively. Ammonium ion is not required and is inhibitory at concentrations above 0.15 M. Magnesium ion inhibited the activity at a concentration as low as 2 mM. Sodium and potassium ions were inhibitory at concentrations above 0.1 M. The molecular activity of tRNA (guanine-1)-methyltransferase was calculated to 10.0 min-1. It was estimated that the enzyme is present at 80 molecules/genome in cells growing with a specific growth rate of 1.0.

Place, publisher, year, edition, pages
1983. Vol. 258, no 2, 1343-1351 p.
National Category
Microbiology in the medical area
URN: urn:nbn:se:umu:diva-32168PubMedID: 6337136OAI: diva2:301549
Available from: 2010-03-03 Created: 2010-03-03 Last updated: 2010-03-12

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