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. 1967 Jan;93(1):315–319. doi: 10.1128/jb.93.1.315-319.1967

Genetically Alterable Transport of Amethopterin in Diplococcus pneumoniae II. Impairment of the System Associated with Various Mutant Genotypes

Francis M Sirotnak 1,2, M Gay Sargent 1,2, Dorris J Hutchison 1,2
PMCID: PMC315004  PMID: 4381316

Abstract

Six mutations determining resistance to amethopterin were examined for their effects on the active transport of the drug. In strains bearing each of the mutations and exhibiting resistance levels varying from 10- to 100-fold, transport at limiting concentrations of H3-amethopterin was reduced from 2.5 to 10 times the rate characteristic of the wild type. Kinetic analysis of transport showed an increase in the value for Km of the system in all of the mutants. Values for the wild-type system were 0.9 × 10−6m and for the mutants varied between 2.5 × 10−6m and 9.0 × 10−6m. Values for Vmax were approximately the same for each system. The mutant transport systems also exhibited a shift in pH optimum from near 6.0 (wild-type) to below 5.0. The results were interpreted as an alteration in the binding properties of the permease in the mutant strains.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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