A unique fold of phospholipase C-β mediates dimerization and interaction with Gαq
A unique fold of phospholipase C-β mediates dimerization and interaction with Gαq
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DOI：
10.1038/nsb731
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发表时间：
2002-01-01
期刊：
影响因子：
--
通讯作者：
Sondek, J
中科院分区：
文献类型：
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作者：
Singer, AU;Waldo, GL;Sondek, J
Gq家族Galpha亚基的GTP结合亚基直接激活磷脂酶C-β(PLC-beta)同工酶，产生第二信使1，4，5-三磷酸肌醇和甘油二酯。PLC-β是GTP酶激活蛋白(GAP)，也促进与GDP结合的非活性Gbeta亚基的形成。由Galpha-GTP亚基激活的磷脂酶和GAP活性都需要PLC-β同工酶特有的C-末端区域。在2.4埃分辨率下测定的禽类PLC-β的C-末端区域的晶体结构揭示了一个新的折叠，该折叠几乎完全由三个长螺旋组成，形成一个螺旋线圈，沿着其长轴以反平行的方向二聚化。二聚体界面广泛(类似于3,200埃(2))，并且，基于凝胶排斥层析，全长PLC-βA是二聚体，表明PLC-βA可能作为二聚体发挥作用。序列保守、突变数据和分子模拟表明，二聚体的静电正表面包含与Gbetaq结合的主要决定因素。正如PLC-Betas所强调的那样，效应器二聚作用为调节与异源三聚体G蛋白相连的信号级联提供了一种可行的机制。
GTP-bound subunits of the Gq family of Galpha subunits directly activate phospholipase C-beta (PLC-beta) isozymes to produce the second messengers inositol 1,4,5-trisphosphate and diacylglycerol. PLC-betas are GTPase activating proteins (GAPs) that also promote the formation of GDP-bound, inactive Gbeta subunits. Both phospholipase activation by Galpha-GTP subunits and GAP activity require a C-terminal region unique to PLC-beta isozymes. The crystal structure of the C-terminal region from an avian PLC-beta, determined at 2.4 Angstrom resolution, reveals a novel fold composed almost entirely of three long helices forming a coiled-coil that dimerizes along its long axis in an antiparallel orientation. The dimer interface is extensive (similar to3,200 Angstrom(2)), and, based on gel exclusion chromatography, full length PLC-betas are dimeric, indicating that PLC-betas likely function as dimers. Sequence conservation, mutational data and molecular modeling show that an electrostatically positive surface of the dimer contains the major determinants for binding Gbetaq. Effector dimerization, as highlighted by PLC-betas, provides a viable mechanism for regulating signaling cascades linked to heterotrimeric G proteins.