title: Multiple drug resistance in the fission yeast Schizosaccharomyces pombe: evidence for the existence of pleiotropic mutations affecting dependent transport systems.
abstract: The uptake of L-tyrosine into wild type and antibiotic resistant strains of Schizosaccharomyces pombe requires an energy source, is initially linear with respect to time, is inhibited by 2,4-dinitrophenol and sodium azide and is saturable. However the initial uptake rates and the amount of L-tyrosine accummulated by antibiotic resistant strains are much less than wild type. Comparison of the kinetic constants of uptake shows that mutant strains have a reduced maximum velocity of uptake compared to wild type and a larger Km. Since the three mutant strains possess a permeability barrier to L-tyrosine as well as being drug resistant this is an indication that antibiotic resistance may be caused by a decrease in plasma membrane permeability.
mesh_terms: D001203:Ascomycota / Q000187:drug effects*; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D003513:Cycloheximide / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D009154:Mutation; D012568:Schizosaccharomyces / Q000187:drug effects* / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D014443:Tyrosine; D003513:Cycloheximide