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

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


  • Han GS
  • Audhya A
  • Markley DJ
  • Emr SD
  • Carman GM


The Journal of biological chemistry

Publication Data

December 6, 2002

Associated Grants

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

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