Structural Insights into Enzyme Regulation for Inositol 1,4,5-Trisphosphate 3-Kinase B
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- 作者：Philip P. Chamberlain ; Mark L. Sandberg ; Karsten Sauer ; Michael P. Cooke ; Scott A. Lesley ; and Glen Spraggon
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：November 8, 2005
- 年：2005
- 卷：44
- 期：44
- 页码：14486 - 14493
- 全文大小：652K
- 年卷期：v.44,no.44(November 8, 2005)
- ISSN：1520-4995
文摘
D-Myoinositol 1,4,5-trisphophate 3-kinases (IP3-3Ks) play important roles in metazoan cellularsignaling. It has been demonstrated that mice without a functional version of IP3-3K isoform B are deficientin peripheral T-cells, indicating that IP3-3KB is essential to the developing immune system. The recentapo IP3-3KA structure exhibited a helix at the catalytic domain N-terminus exhibited a helix at theN-terminus of the catalytic domain, with a tryptophan indole moiety mimicking the binding mode of thesubstrate ATP purine ring, suggesting a mechanism of autoinhibition. Here we present the structure ofthe complete catalytic domain of IP3-3KB, including the CaM binding domain in complex with Mg2+ andATP. The crystal structure reveals a homodimeric arrangement of IP3-3KB catalytic domains, mediatedvia an intermolecular antiparallel 
-sheet formed from part of the CaM binding region. Residues from theputative autoinhibitory helix are rearranged into a loop configuration, with extensive interactions with thebound ATP. Mutagenesis of residues from this region reveals that substitution of the putative autoinhibitorytryptophan generates a hyperactive enzyme which retains Ca2+/CaM sensitivity. The IP3-3KB structuresuggests a mechanism of enzyme activation, and raises the possibility that an interaction between IP3-3KB molecules may occur as part of the catalytic or regulatory cycle.
-sheet formed from part of the CaM binding region. Residues from theputative autoinhibitory helix are rearranged into a loop configuration, with extensive interactions with thebound ATP. Mutagenesis of residues from this region reveals that substitution of the putative autoinhibitorytryptophan generates a hyperactive enzyme which retains Ca2+/CaM sensitivity. The IP3-3KB structuresuggests a mechanism of enzyme activation, and raises the possibility that an interaction between IP3-3KB molecules may occur as part of the catalytic or regulatory cycle.