The recBC Enzyme of Escherichia coli K12: Premature Cessation of Catalytic Activities in vitro and Reactivation by Potassium Ions

Thymine-requiring strains of Escherichia coli suppress nonsense and frame-shift mutations. This appears to occur during translation, suggesting that the lack of activity of an enzyme thymidylate synthase, required for the synthesis of a DNA precursor, alters the fidelity of translation. The aminoglycoside antibiotic kasugamycin, which enhances translational accuracy in vitro, prevents thymine-requiring cells from suppressing. The inhibition of suppression by kasugamycin is not prevented by the introduction of two different kasugamycin-resistance mutations, although the dose required for inhibition increases. These observations support the conclusion that suppression occurs during translation.Key words: suppression, kasugamycin, translation, thymine-requiring.

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Purification and some properties of nitrate reductase (EC 1.7.99.4) from Escherichia coli K12

Biochemical Journal ◽

10.1042/bj1530533 ◽

1976 ◽

Vol 153 (3) ◽

pp. 533-541 ◽

Cited By ~ 39

Author(s):

R A Clegg

Keyword(s):

Escherichia Coli ◽

Aqueous Solution ◽

Nitrate Reductase ◽

Cell Envelope ◽

Purification Procedure ◽

Benzyl Viologen ◽

Escherichia Coli K12 ◽

Enzyme Subunits ◽

Triton X

1. Nitrate reductase was purified 134-fold from Escherichia coli K12. The purification procedure involves the release by Triton X-100 of the enzyme from the cell envelope. i. The purified enzyme exists in aqueous solution either as a monomer (mol. wt. about 220 000) or as an associated form (probably a tetramer; mol.wt. about 880 000). 3. The purified enzyme has three subunits with apparent mol.wts. of 150 000, 67000 and 65000. An additional subunit of apparent mol.wt. 20000 is present in a haem-containing fraction that is also produced by the preparative procedure described. 4. None of the enzyme subunits is present in the cell envelope of cells grown in the absence of nitrate. 5. Reversible changes in the activity of nitrate reductase in vitro with FMNH2 as reductant can be induced under circumstances which are without effect on the reduced Benzyl Viologen-NO3-activity.

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Studies in vitro of the Enzyme Controlled by the recB and recC Genes of Escherichia coli K12

Biochemical Society Transactions ◽

10.1042/bst0010237 ◽

1973 ◽

Vol 1 (1) ◽

pp. 237-238

Author(s):

STUART LINN ◽

ALEXANDER E. KARU ◽

PETER J. GOLDMARK

Keyword(s):

Escherichia Coli ◽

Escherichia Coli K12

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A possible mechanism for the in vitro activation of L-serine deaminase activity in Escherichia coli K12

Biochemistry and Cell Biology ◽

10.1139/o90-104 ◽

1990 ◽

Vol 68 (4) ◽

pp. 723-728 ◽

Cited By ~ 4

Author(s):

E. B. Newman ◽

Caroline Walker ◽

K. Ziegler-Skylakakis

Keyword(s):

Escherichia Coli ◽

Enzyme Activation ◽

Free Radical Scavengers ◽

Escherichia Coli K12 ◽

Diethylene Triamine ◽

In Vitro Activation ◽

Diethylene Triamine Pentaacetic Acid ◽

Serine Deaminase ◽

Reversible Reduction

L-Serine deaminase is inactive in crude extracts of Escherichia coli K12, but can be activated by incubation with iron and dithiothreitol. This activation requires oxygen, and is inhibited by free radical scavengers and by diethylene triamine pentaacetic acid, which prevents Fe cycling. We suggest that in vitro activation of L-serine deaminase is catalyzed by an oxidant (perhaps hydroxyl radicals). Also, activation may be accompanied by a decrease in molecular weight and involve both a cleavage of the polypeptide chain and a reversible reduction of the molecule.Key words: enzyme activation, serine degradation.

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