Properties of an Escherichia coli K-12 mutant defective in the transport of arginine and ornithine

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Abstract
A canavanine-resistant mutant strain, defective in the transport of arginine and ornithine, was isolated and characterized. The kinetics of influx and the steady state of accumulation of arginine and ornithine are affected by the mutation, but the activity of other related transport systems remains unchanged. Competitive studies showed that L-canavanine can inhibit efficiently the arginine-specific uptake system. D-Arginine appears to be a moderate inhibitor. None of the basic amino acid-binding proteins of the mutant strain showed detectable alterations in terms of quantity, physical properties or affinity constants. Studies on the relationship between the number of transport carriers and the steady state of accumulation of arginine suggested the presence of a reduced number of membrane carriers in the mutant strain. The mutation probably affects a regulatory gene concerned with controlling the amount of membrane carriers produced, which are components of the arginine- and ornithine-specific uptake systems. The mutation maps at 62 min on the recalibrated linkage map of E. coli K-12, in a locus closely linked or identical to argP.