1w2c | pdb_00001w2c
HUMAN INOSITOL (1,4,5) TRISPHOSPHATE 3-KINASE COMPLEXED WITH MN2+/AMPPNP/INS(1,4,5)P3
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| 1w2c, resolution 1.95Å | |||||||||||||
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| Sites: | AC1 | ||||||||||||
| Ligands: | ANP, I3P, MN, SO4 | ||||||||||||
| Activity: | Transferase, with EC number 2.1.7.127 | ||||||||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||||||||
Overview
Mammalian cells produce a variety of inositol phosphates (InsPs), including Ins(1,4,5)P3 that serves both as a second messenger and as a substrate for inositol polyphosphate kinases (IPKs), which further phosphorylate it. We report the structure of an IPK, the human Ins(1,4,5)P3 3-kinase-A, both free and in complexes with substrates and products. This enzyme catalyzes transfer of a phosphate from ATP to the 3-OH of Ins(1,4,5)P3, and its X-ray crystal structure provides a template for understanding a broad family of InsP kinases. The catalytic domain consists of three lobes. The N and C lobes bind ATP and resemble protein and lipid kinases, despite insignificant sequence similarity. The third lobe binds inositol phosphate and is a unique four-helix insertion in the C lobe. This lobe embraces all of the phosphates of Ins(1,4,5)P3 in a positively charged pocket, explaining the enzyme's substrate specificity and its inability to phosphorylate PtdIns(4,5)P2, the membrane-resident analog of Ins(1,4,5)P3.
About this Structure
1W2C is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Structure of a human inositol 1,4,5-trisphosphate 3-kinase: substrate binding reveals why it is not a phosphoinositide 3-kinase., Gonzalez B, Schell MJ, Letcher AJ, Veprintsev DB, Irvine RF, Williams RL, Mol Cell. 2004 Sep 10;15(5):689-701. PMID:15350214
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