Inositol pyrophosphates are relatively poorly understood, highly phosphorylated members of the inositol polyphosphate family. Two studies describe related advances in signaling involving inositol pyrophosphates. Mulugu et al. purified an inositol pyrophosphate synthase from yeast, called Vip1. Lee et al. purified a molecule that regulates the yeast Pho80-Pho85-Pho81 complex, a protein complex containing a cyclin, a cyclin-dependent kinase (CDK), and a CDK inhibitor. The active molecule turned out to be myo-D-inositol heptakisphosphate (IP7), which is synthesized through the kinase activity of Vip1.
S. Mulugu, W. Bai, P. C. Fridy, R. J. Bastidas, J. C. Otto, D. E. Dollins, T. A. Haystead, A. A. Ribeiro, J. D. York, A conserved family of enzymes that phosphorylate inositol hexakisphosphate. Science 316, 106-109 (2007). [Abstract] [Full Text]