E-Syt2 串联 C₂ 结构域的结构和 Ca²⁺结合特性。
Structure and Ca²⁺-binding properties of the tandem C₂ domains of E-Syt2.
机构信息
Department of Biophysics, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390, USA.
Department of Molecular and Cellular Physiology, Stanford University Medical School, 265 Campus Drive, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University Medical School, 265 Campus Drive, Stanford, CA 94305, USA.
出版信息
Structure. 2014 Feb 4;22(2):269-80. doi: 10.1016/j.str.2013.11.011. Epub 2013 Dec 26.
Contacts between the endoplasmic reticulum and the plasma membrane involve extended synaptotagmins (E-Syts) in mammals or tricalbins in yeast, proteins with multiple C₂ domains. One of the tandem C₂ domains of E-Syt2 is predicted to bind Ca²⁺, but no Ca²⁺-dependent function has been attributed to this protein. We have determined the crystal structures of the tandem C₂ domains of E-Syt2 in the absence and presence of Ca²⁺ and analyzed their Ca²⁺-binding properties by nuclear magnetic resonance spectroscopy. Our data reveal an unexpected V-shaped structure with a rigid orientation between the two C₂ domains that is not substantially altered by Ca²⁺. The E-Syt2 C2A domain binds up to four Ca²⁺ ions, whereas the C₂B domain does not bind Ca²⁺. These results suggest that E-Syt2 performs an as yet unidentified Ca²⁺-dependent function through its C₂A domain and uncover fundamental differences between the properties of the tandem C₂ domains of E-Syts and synaptotagmins.
内质网和质膜之间的联系涉及哺乳动物中的延伸突触结合蛋白（E-Syts）或酵母中的三联钙结合蛋白（tricalbins），这些蛋白质都具有多个 C₂ 结构域。E-Syt2 的串联 C₂ 结构域之一被预测能结合 Ca²⁺，但尚未确定该蛋白具有 Ca²⁺依赖性功能。我们测定了无 Ca²⁺和有 Ca²⁺存在时 E-Syt2 的串联 C₂ 结构域的晶体结构，并通过核磁共振波谱分析了它们的 Ca²⁺结合特性。我们的数据揭示了一个意想不到的 V 形结构，两个 C₂ 结构域之间具有刚性的定向，这种结构在 Ca²⁺存在下不会发生实质性改变。E-Syt2 的 C2A 结构域可结合多达四个 Ca²⁺离子，而 C₂B 结构域不结合 Ca²⁺。这些结果表明，E-Syt2 通过其 C2A 结构域执行一个尚未确定的 Ca²⁺依赖性功能，并揭示了 E-Syts 和突触结合蛋白的串联 C₂ 结构域之间的性质存在根本差异。
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