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Inositol 1,3,4,5,6-pentakisphosphate 2-kinase is a distant IPK member with a singular inositide binding site for axial 2-OH recognition
Beatriz González, Jose Ignacio Baños-Sanz, Maider Villate, Charles Alistair Brearley, Julia Sanz-Aparicio and Susan S. Taylor
Proceedings of the National Academy of Sciences of the United States of America
Vol. 107, No. 21 (May 25, 2010), pp. 9608-9613
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25681647
Page Count: 6
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Inositol phosphates (InsPs) are signaling molecules with multiple roles in cells. In particular Ins(1,2,3,4,5,6)P₆ (InsP₆) is involved in mRNA export and editing or chromatin remodeling among other events. InsP₆ accumulates as mixed salts (phytate) in storage tissues of plants and plays a key role in their physiology. Human diets that are exclusively grain-based provide an excess of InsP₆ that, through chelation of metal ions, may have a detrimental effect on human health. Ins(1,3,4,5,6)P₅ 2-kinase (InsP₅ 2-kinase or Ipk1) catalyses the synthesis of InsP₆ from InsP₅ and ATP, and is the only enzyme that transfers a phosphate group to the axial 2-OH of the myo-inositide. We present the first structure for an InsP₅ 2-kinase in complex with both substrates and products. This enzyme presents a singular structural region for inositide binding that encompasses almost half of the protein. The key residues in substrate binding are identified, with Asp368 being responsible for recognition of the axial 2-OH. This study sheds light on the unique molecular mechanism for the synthesis of the precursor of inositol pyrophosphates.
Proceedings of the National Academy of Sciences of the United States of America © 2010 National Academy of Sciences