title: Chitin synthetase mutants of Phycomyces blakesleeanus.
abstract: Mutants resistant to nikkomycin, an inhibitor of chitin biosynthesis, were isolated after exposure of wild-type spores of the fungus Phycomyces blakesleeanus to N-methyl-N'-nitro-N-nitrosoguanidine. Genetic analysis revealed that nikkomycin resistance was due to mutations in a single gene, chsA. Mutants and wild type grew equally well in the absence of nikkomycin. In contrast to the wild type, whose spore germination and mycelial growth were inhibited by 5 microM nikkomycin, chsA mutants grew reasonably well in the presence of 50 microM nikkomycin. Chitin synthesis in vivo was much less affected by the drug in the mutants than in the wild type. Resistance was not due to impaired uptake or detoxification of the drug. Analysis of the kinetics of chitin synthesis in vitro showed that the mutants had a decreased Ka for the allosteric activator, N-acetylglucosamine, and gross alterations in nikkomycin inhibition kinetics. These results indicate that chsA is the structural gene for chitin synthetase, or at least for the polypeptide that bears the catalytic and allosteric sites.
authors.affiliation: Departamento de Genética, Universidad de Sevilla, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Cubero
authors.forename: J
authors.initials: J
authors.lastname: Ruiz-Herrera
authors.forename: E
authors.initials: E
authors.lastname: Cerdá-Olmedo
mesh_terms: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D000935:Antifungal Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D002687:Chitin Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics; D009154:Mutation / Q000502:physiology*; D010800:Phycomyces / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D011995:Recombination, Genetic / Q000235:genetics
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; C011952:nikkomycin; D002687:Chitin Synthase