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J. Bacteriol., 08 1995, 4557-4561, Vol 177, No. 15
AA Guffanti and TA Krulwich
The properties of TetA(L)-dependent tetracycline/proton and Na+/proton
antiport were studied in energized everted vesicles of Escherichia coli
transformed with a cloned tetA(L) gene (pJTA1) from Bacillus subtilis.
Inhibition patterns by valinomycin and nigericin indicated that both
antiports were electrogenic, in contrast to the tetracycline/proton
antiport encoded by gram-negative plasmid tet genes. Tetracycline uptake in
the everted system was dependent upon a divalent cation, with cobalt being
the preferred one. The apparent Km for tetracycline was markedly increased
at pH 8.5 versus pH 7.5, whereas the Vmax was unchanged. The much higher
apparent Km for Na+ decreased at pH 8.5 relative to that at pH 7.5, as did
the Vmax. Na+ did not affect tetracycline uptake, nor did Co2+ and/or
tetracycline affect Na+ uptake; complex patterns of inhibition by amiloride
and analogs thereof were observed.
Copyright © 1995, American Society for Microbiology
Tetracycline/H+ antiport and Na+/H+ antiport catalyzed by the Bacillus subtilis TetA(L) transporter expressed in Escherichia coli
Department of Biochemistry, Mount Sinai School of Medicine of CUNY, New York 10029, USA.
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