Trinucleotide Insertions, Deletions, and Point Mutations in Glucose Transporters Confer K+ Uptake in Saccharomyces cerevisiae
AUTOR(ES)
Liang, Hong
FONTE
American Society for Microbiology
RESUMO
Deletion of TRK1 and TRK2 abolishes high-affinity K+ uptake in Saccharomyces cerevisiae, resulting in the inability to grow on typical synthetic growth medium unless it is supplemented with very high concentrations of potassium. Selection for spontaneous suppressors that restored growth of trk1Δ trk2Δ cells on K+-limiting medium led to the isolation of cells with unusual gain-of-function mutations in the glucose transporter genes HXT1 and HXT3 and the glucose/galactose transporter gene GAL2. 86Rb uptake assays demonstrated that the suppressor mutations conferred increased uptake of the ion. In addition to K+, the mutant hexose transporters also conferred permeation of other cations, including Na+. Because the selection strategy required such gain of function, mutations that disrupted transporter maturation or localization to the plasma membrane were avoided. Thus, the importance of specific sites in glucose transport could be independently assessed by testing for the ability of the mutant transporter to restore glucose-dependent growth to cells containing null alleles of all of the known functional glucose transporter genes. Twelve sites, most of which are conserved among eukaryotic hexose transporters, were revealed to be essential for glucose transport. Four of these have previously been shown to be essential for glucose transport by animal or plant transporters. Eight represented sites not previously known to be crucial for glucose uptake. Each suppressor mutant harbored a single mutation that altered an amino acid(s) within or immediately adjacent to a putative transmembrane domain of the transporter. Seven of 38 independent suppressor mutations consisted of in-frame insertions or deletions. The nature of the insertions and deletions revealed a striking DNA template dependency: each insertion generated a trinucleotide repeat, and each deletion involved the removal of a repeated nucleotide sequence.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=108804Documentos Relacionados
- Effect of insertions, deletions, and double-strand breaks on homologous recombination in mouse L cells.
- Generation of single base-pair deletions, insertions, and substitutions by a site-specific recombination system.
- Evolution of feline leukemia virus variant genomes with insertions, deletions, and defective envelope genes in infected cats with tumors.
- TRK1 and TRK2 encode structurally related K+ transporters in Saccharomyces cerevisiae.
- Haemophilia B: database of point mutations and short additions and deletions, 7th edition.