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The Saccharomyces cerevisiae LSB6 gene encodes phosphatidylinositol 4-kinase activity.

http://www.ncbi.nlm.nih.gov/pubmed/12361950

The LSB6 gene product was identified from the Saccharomyces Genome Data Base (locus YJL100W) as a putative member of a novel type II phosphatidylinositol (PI) 4-kinase family. Cell extracts lacking the LSB6 gene had a reduced level of PI 4-kinase activity. In addition, multicopy plasmids containing the LSB6 gene directed the overexpression of PI 4-kinase activity in cell extracts of wild-type cells, in an lsb6Delta mutant, in a pik1(ts) stt4(ts) double mutant, and in an pik1(ts) stt4(ts) lsb6Delta triple mutant. The heterologous expression of the S. cerevisiae LSB6 gene in Escherichia coli resulted in the expression of a protein that possessed PI 4-kinase activity. Although the lsb6Delta mutant did not exhibit a growth phenotype and failed to exhibit a defect in phosphoinositide synthesis in vivo, the overexpression of the LSB6 gene could partially suppress the lethal phenotype of an stt4Delta mutant defective in the type III STT4-encoded PI 4-kinase indicating that Lsb6p functions as a PI 4-kinase in vivo. Lsb6p was localized to the membrane fraction of the cell, and when overexpressed, GFP-tagged Lsb6p was observed on both the plasma membrane and the vacuole membrane. The enzymological properties (pH optimum, dependence on magnesium or manganese as a cofactor, the dependence of activity on Triton X-100, the dependence on the PI surface concentration, and temperature sensitivity) of the LSB6-encoded enzyme were very similar to the membrane-associated 55-kDa PI 4-kinase previously purified from S. cerevisiae.

Pubmed ID: 12361950 RIS Download

Mesh terms: 1-Phosphatidylinositol 4-Kinase | Adenosine Triphosphate | Cell Division | DNA | Databases as Topic | Detergents | Dose-Response Relationship, Drug | Electrophoresis, Polyacrylamide Gel | Escherichia coli | Hot Temperature | Hydrogen-Ion Concentration | Immunoblotting | Intracellular Membranes | Magnesium | Manganese | Microscopy, Fluorescence | Mutation | Octoxynol | Phenotype | Polymerase Chain Reaction | Protein Binding | Saccharomyces cerevisiae | Sodium Chloride | Subcellular Fractions | Temperature | Vacuoles

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Associated grants

  • Agency: NCI NIH HHS, Id: CA-58689
  • Agency: NIGMS NIH HHS, Id: GM-28140

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