Inhibition of Proline Synthesis by Tetracycline in Escherichia coli

JOURNAL OF BACTERIOLOGY, Jan. 1968, p. 257-258 Copyright © 1968 American Society for Microbiology

Vol. 95, No.1 Printed in U.S.A.

Inhibition of Proline Synthesis by Tetracycline in Escherichia coli ANNETTE BAICH AND ALLAN HYTOWITZ Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331

Received for publication 9 October 1967

Proline is synthesized from glutamic acid by way of the intermediate glutamic -y-semialdehyde, as in the following equation: glutamic acid + glutamic 'y-semialdehyde -* proline. In Escherichia coli W, the first reaction is subject to endproduct inhibition by proline (A. Baich and D. J. Pierson, Biochim. Biophys. Acta 104:397, 1965). This reaction is also inhibited by low, although higher than bacteriostatic, concentrations of chloramphenicol and streptomycin (A. Baich, Bacteriol. Proc., p. 83, 1966). End-product inhibition and susceptibility to antibiotics are evidently correlated, because a decrease in sensitivity to proline is invariably accompanied by a decrease in sensitivity to antibiotics. We now find that the synthesis of glutamic 'y-semialdehyde, and, thus, of proline, is sensitive to bacteriostatic concentrations of tetracycline,

ce 0

(0' wP 0

of tetra cycl ine

FIG. 2. Effect of tetracycline on growth of Escherichia coili strains. Strain WPJ is a derivative of the wildtype W and differs from the wild type in that it lacks control of proline biosynthesis. The growth experiments were carried out in synthetic medium.

and the wild type is 40 times more sensitive to tetracycline than is a presumably isogenic control deficient strain. To reduce the rate of glutamic Py-semialdehyde production by 50%, 0.07 X 104 M (0.5 ,ug/ml) tetracycline is required by the wild type, and 3 X 10 4 M (20 ,ug/ml) is required for a control deficient strain (Fig. 1). Nevertheless, the growth rates of both strains are equally susceptible to tetracycline: 0.07 X 10-4 M reduced the rates of both the wild type and control 'oncentration of tetracycline deficient strains by 50% (Fig. 2). The effect of tetracycline on the synthesis of FIG. 1. Effect of tetracycline on the production of glutamic -y-semialdehyde by strains of Escherichia coli proline is similar to the effect of this antibiotic on W. (The tetracycline used in these experiments was a the synthesis of anthranilic acid (F. Gibson, M. J. generous gift from The Upjohn Co., Kalamazoo, Jones, and H. Teltscher, Nature 176:164, 1955; Mich.) Strains 55-1 and WPI-30 lack pyrolline-5- F. Gibson and B. McDougall, Australian J. carboxylate dehydrogenase, and both excrete glutamic Exptl. Biol. Med. Sci. 39:171, 1961). Because of -y-semialdehyde into the medium. The production of the similarities of these observations, it seems glutamic -y-semialdehyde by strain 55-1 is subject to likely that the antibiotic affects the action of the end-product inhibitionz by proline, whereas that of indicated enzymes indirectly, possibly by binding WPI-30 is not. The details of the conditions for growth and excretion measurements were described by to the cell membrane and thereby altering the A. Baich and D. J. Pierson (Biochim. Biophys. Acta configuration of the membrane-bound enzymes. The enzyme in the proline control deficient strain 104: 397, 1965). 257

258

NOTES

be less subject to this configurational change, alternatively, it may not be bound to the membrane. This may be significant, since, in both pathways, it is the production of the first product committed to that pathway which is inhibited by the antibiotic.

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J. BACTERIOL.

This investigation was supported by Public Health Service grant CA-02295 from the National Cancer Institute. One of us (A. B.) is the grateful recipient of a Research Career Development award from the Public Health Service, National Institute of Allergy and Infectious Diseases.