Phosphatidylinositol-4-Kinase Catalytic Alpha (PI4Ka)

PI4Ka catalyzes the first committed step in the biosynthesis of phosphatidylinositol 4,5-bisphosphate. The mammalian PI 4-kinases have been classified into two types, II and III, based on their molecular mass, and modulation by detergent and adenosine. Two transcript variants encoding different isoforms have been described for this gene.The predicted 854-amino acid protein has a calculated molecular mass of 97 kD. It contains an ankyrin repeat, a lipid kinase unique domain, a pleckstrin-homology domain, and a lipid kinase catalytic domain. PI4K-alpha has high amino acid sequence similarity to the yeast PI 4-kinases STT4 and PIK1; it has less amino acid sequence similarity to the catalytic domains of mammalian and yeast PI 3-kinases and to the yeast TOR family of proteins.