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pubmed:abstractText |
1. After incubation of Escherichia coli with N-iodo[1,2-(14)C(2)]acetylglucosamine, 95-99% of the (14)C taken up by whole cells is located in a cold-trichloroacetic acid-soluble fraction. Two major components of this fraction are S-carboxymethylcysteine and S-carboxymethylglutathione. The same compounds accumulate during incubation with iodo[(14)C]acetate but not with iodo[(14)C]acetamide. The amount of (14)C associated with a cold-trichloroacetic acid-insoluble fraction are comparable for all three alkylating agents. After incubation with iodo[(14)C]acetamide, 50% of the label bound to whole cells is recoverable in a cold-trichloroacetic acid-insoluble fraction. 2. Uptake and incorporation of (14)C from [U-(14)C]glycerol is blocked at an early stage by N-iodoacetylglucosamine. No specific inhibition of macromolecular synthesis could be demonstrated. 3. Mutants selected for resistance to iodoacetate are partially resistant to iodoacetate and N-iodoacetylglucosamine, but show no resistance to iodoacetamide. 4. Mutants selected for resistance to N-iodoacetylglucosamine are not resistant to iodoacetate or iodoacetamide, and are defective in their ability to grow on N-acetylglucosamine. Resistance to N-iodoacetylglucosamine is not absolute, and depends on the presence of glucose or certain other sugars; there is no resistance during growth on maltose, glycerol or succinate. 5. Absolute resistance can be achieved by selecting for a second mutation conferring resistance during growth on maltose; double mutants isolated by this procedure are unable to grow on N-acetylglucosamine and grow poorly on glucosamine. Resistant single mutants have a slightly diminished uptake of N-acetyl[1-(14)C]glucosamine, but in resistant double mutants the uptake of both [1-(14)C]glucosamine and N-acetyl[1-(14)C]glucosamine is severely diminished. 6. These observations are consistent with the presence of two permeases for N-acetylglucosamine, one that also permits uptake of glucosamine and another that allows entry of methyl 2-acetamido-2-deoxy-alpha-d-glucoside. N-Iodoacetylglucosamine can gain entry to the cell by both permeases.
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