The molecular basis for cyclopiazonic acid inhibition of the sarcoplasmic reticulum calcium pump
The molecular basis for cyclopiazonic acid inhibition of the sarcoplasmic reticulum calcium pump
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DOI：
10.1074/jbc.m611653200
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发表时间：
2007-03-30
影响因子：
4.8
通讯作者：
Young, Howard S.
中科院分区：
文献类型：
--
作者：
Moncoq, Karine;Trieber, Catharine A.;Young, Howard S.
肌浆网 Ca2+-ATP 酶对于肌肉收缩-舒张周期中钙的再摄取至关重要。在这里，我们展示了在 2.65 埃分辨率下结合环吡嗪酸 (CPA) 和氟化镁的无钙态结构，以及在 3.4 埃分辨率下结合 CPA 和 ADP 的无钙态结构。在这两种结构中，CPA 占据由跨膜片段 M1-M4 界定的钙通道。 Ca2+-ATP酶的抑制通过围绕CPA特特拉姆酸的极性口袋和支撑抑制剂的疏水平台来稳定。涉及的钙泵残基包括Gln(56)、Leu(61)、Val(62)和Asn(101)。我们得出结论，CPA 通过阻断钙进入通道并固定一部分跨膜螺旋来抑制钙泵。在 E2(CPA) 结构中，ADP 以不同的方向结合在核苷酸结合袋内。腺嘌呤环夹在核苷酸结合结构域的 Arg(489) 和磷酸化结构域的 Arg(678) 之间。这种结合模式符合 ATP 依赖性蛋白质中常见的腺嘌呤识别基序。
The sarcoplasmic reticulum Ca2+-ATPase is essential for calcium reuptake in the muscle contraction-relaxation cycle. Here we present structures of a calcium-free state with bound cyclopiazonic acid (CPA) and magnesium fluoride at 2.65 angstrom resolution and a calcium-free state with bound CPA and ADP at 3.4 angstrom resolution. In both structures, CPA occupies the calcium access channel delimited by transmembrane segments M1-M4. Inhibition of Ca2+-ATPase is stabilized by a polar pocket that surrounds the tetramic acid of CPA and a hydrophobic platform that cradles the inhibitor. The calcium pump residues involved include Gln(56), Leu(61), Val(62), and Asn(101). We conclude that CPA inhibits the calcium pump by blocking the calcium access channel and immobilizing a subset of transmembrane helices. In the E2(CPA) structure, ADP is bound in a distinct orientation within the nucleotide binding pocket. The adenine ring is sandwiched between Arg(489) of the nucleotide-binding domain and Arg(678) of the phosphorylation domain. This mode of binding conforms to an adenine recognition motif commonly found in ATP-dependent proteins.