KNQ1, a Kluyveromyces lactis gene encoding a drug efflux permease.
Several transport systems play an important role in conferring multiple drug resistance, presumably due to their catalysis of the energy-dependent extrusion of a large number of structurally and functionally unrelated compounds out of the cells. In the present work, the gene named KNQ1 (encoding Kluyveromyces lactis membrane permease) was cloned by functional complementation of the cycloheximide-hypersensitivity phenotype of the Saccharomyces cerevisiae mutant strain lacking a functional PDR5 gene. The isolated gene exhibited 48.9% identity with the S. cerevisiae ATR1 gene conferring resistance to aminotriazole and 4-nitroquinoline- N-oxide and encoded a protein of 553 amino acids. When present in multicopy, it efficiently complemented the phenotype associated with the Delta pdr5 or Delta pdr1Delta pdr3 mutations in S. cerevisiae. Overexpression of the KNQ1 gene in K. lactis wild-type strains led to resistance against several cytotoxic compounds, like 4-nitroquinoline- N-oxide, 3-aminotriazole, bifonazole and ketoconazole. The gene was assigned to K. lactis chromosome III and its expression was found to be responsive to oxidative stress induced by hydrogen peroxide. Based on the phenotype of homologous and heterologous transformants, we propose that the gene encodes a membrane-associated component of the machinery responsible for decreasing the concentration of several toxic compounds in the cytoplasm of yeast cells.
Faculty of Natural Sciences, Department of Microbiology and Virology, Comenius University in Bratislava, Mlynska dolina B-2, 842 15, Bratislava, Slovak Republic.
Maria
M
Takacova
Denisa
D
Imrichova
Jana
J
Cernicka
Yvetta
Y
Gbelska
Julius
J
Subik
D015825:Chromosomes, Fungal / Q000235:genetics; D003001:Cloning, Molecular; D025141:Drug Resistance, Fungal / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D017353:Gene Deletion; D005800:Genes, Fungal / Q000235:genetics*; D005816:Genetic Complementation Test; D007716:Kluyveromyces / Q000201:enzymology* / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D020161:Physical Chromosome Mapping; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
C108080:ATR1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins