| Abstract: | Three temperature-sensitive alleles of benA (benA11, 17 and 21) confer resistance to growth inhibition by p-fluorophenylalanine (FPA). FPA resistance cosegregates with the benA gene. Two back-mutations in benA which cause loss of temperature sensitivity cause loss of FPA resistance, and two indirect suppressors of benA temperature sensitivity also cause FPA resistance to be lost. These results indicate that FPA resistance is an intrinsic property of the benA mutations. The intracellular phenylalanine concentrations of these strains are normal as is their ability to take up phenylalanine from the medium. We conclude that FPA must inhibit growth and cause non-disjunction by a direct effect on the polymerization of tubulin. |
