Arabidopsis Synaptotagmin SYT1, a Type I Signal-anchor Protein, Requires Tandem C2 Domains for Delivery to the Plasma Membrane*
Arabidopsis Synaptotagmin SYT1, a Type I Signal-anchor Protein, Requires Tandem C2 Domains for Delivery to the Plasma Membrane*
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DOI：
10.1074/jbc.m109.084046
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发表时间：
2010-05
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影响因子：
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通讯作者：
T. Yamazaki;N. Takata;M. Uemura;Y. Kawamura
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文献类型：
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作者：
T. Yamazaki;N. Takata;M. Uemura;Y. Kawamura
完整的膜蛋白正确定位于亚细胞室对于它们的功能是重要的。突触素含有一个跨膜结构域，在其N端起I型信号锚序列的作用，在其C端有两个钙结合结构域(C2a和C2b)。在这里，我们证明了拟南芥Synaptopagmin同系物SYT1在质膜(PM)上的定位是由串联的C2结构域调制的。对由天然SYT1启动子驱动的转化子表达绿色荧光蛋白标记的SYT1的根分析表明，SYT1是在内质网合成的，然后通过胞吐途径输送到PM。我们在原生质体中瞬时表达了一系列截短的蛋白质，并确定了串联的C2a-C2b结构域是SYT1定位到PM所必需的根据与其他同源物的序列比较，在C2B结构域的钙结合基序突变后，SYT1的PM定位大大降低，例如内膜定位的SYT5。在植物突触素分子进化中发生的功能分化可能需要将SYT1定位到PM。
The correct localization of integral membrane proteins to subcellular compartments is important for their functions. Synaptotagmin contains a single transmembrane domain that functions as a type I signal-anchor sequence in its N terminus and two calcium-binding domains (C2A and C2B) in its C terminus. Here, we demonstrate that the localization of an Arabidopsis synaptotagmin homolog, SYT1, to the plasma membrane (PM) is modulated by tandem C2 domains. An analysis of the roots of a transformant-expressing green fluorescent protein-tagged SYT1 driven by native SYT1 promoter suggested that SYT1 is synthesized in the endoplasmic reticulum, and then delivered to the PM via the exocytotic pathway. We transiently expressed a series of truncated proteins in protoplasts, and determined that tandem C2A-C2B domains were necessary for the localization of SYT1 to the PM. The PM localization of SYT1 was greatly reduced following mutation of the calcium-binding motifs of the C2B domain, based on sequence comparisons with other homologs, such as endomembrane-localized SYT5. The localization of SYT1 to the PM may have been required for the functional divergence that occurred in the molecular evolution of plant synaptotagmins.