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Repression-Dependent Alteration of an Arginine Enzyme in Escherichia coli

Thomas Leisinger, Ruth H. Vogel and Henry J. Vogel
Proceedings of the National Academy of Sciences of the United States of America
Vol. 64, No. 2 (Oct. 15, 1969), pp. 686-692
Stable URL: http://www.jstor.org/stable/59803
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Repression-Dependent Alteration of an Arginine Enzyme in Escherichia coli
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Abstract

Treatment of susceptible Escherichia coli K12 derivatives with 0.4 M Mg++ at 37 degrees, potentiated by L-arginine or L-canavanine, leads to alteration of acetylornithine δ -transaminase. The alteration, obtained in the absence of protein synthesis and reversible at 0 or 37 degrees, is manifested in extracts by lowered activity and modified substrate affinity behavior of the enzyme without gross changes in sedimentation properties. Cells grown under arginine repression are susceptible to the treatment; cells grown under genetic or steady-state physiological derepression are not. Transaminase synthesized during early derepression can be altered, although to progressively diminishing extents. Enzyme formed under steady-state derepression becomes alterable following transition to repression. The Mg++-dependent alteration can be thought to arise while the enzyme, arginine (or canavanine), and aporepressor are in contact, and to reflect a physiological process such as the participation of the enzyme in the repressive complex.

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