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J Bacteriol. 1968 January; 95(1): 113-122
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Ion Metabolism in a Potassium Accumulation Mutant of Escherichia coli B I. Potassium Metabolism

^a Physiological Chemistry Section, Bioscience Branch, U.S. Air Force School of Aerospace Medicine, Brooks AFB, Texas 78235

ABSTRACT

A potassium transport mutant of Escherichia coli is described which is deficient in the intake of potassium. The phenotype of this mutant is characterized by (i) failure to grow in K⁺-deficient medium, (ii) failure to accumulate K⁺ in K⁺-deficient medium, (iii) a steady-state intracellular K⁺ that varies sigmoidally with the medium K⁺ concentration, (iv) a signoidally shaped rate-concentration curve and a curved reciprocal plot for net K⁺ uptake kinetics, and (v) a low steady-state flux of potassium associated with a reduced influx rate constant. The data are discussed in terms of the present day models of cation transport. These models have led to four possible explanations of the mutant's phenotype: (i) a selectivity reversal such that intracellular cation binding sites bind another cation instead of K⁺; (ii) a structural alteration of cation binding cell proteins so that K⁺ is bound by "cooperative binding" (sigmoid isotherm) instead of by simple adsorption (hyperbolic isotherm); (iii) conversion of an enzyme in intermediate metabolism that rate-limits K⁺ uptake to an allosteric protein; (iv) conversion of the "carrier protein" for K⁺ to an allosteric protein.

¹ Present address: Biophysical Laboratory, Department of Internal Medicine, State University of New York Downstate Medical Center, Brooklyn, N.Y.

This article has been cited by other articles:

• Damadian, R. (1969). Ion Exchange in Escherichia coli: Potassium-Binding Proteins. Science 165: 79-81 [Abstract]