二价阳离子对磷脂与突触结合蛋白III的C2A结构域结合的调节作用。
Regulation by bivalent cations of phospholipid binding to the C2A domain of synaptotagmin III.
作者信息
Fukuda M, Kojima T, Mikoshiba K
机构信息
Molecular Neurobiology Laboratory, Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan.
出版信息
Biochem J. 1997 Apr 15;323 ( Pt 2)(Pt 2):421-5. doi: 10.1042/bj3230421.
Synaptotagmins are Ca2+-and phospholipid-binding proteins of synaptic vesicles that might function as Ca2+ receptors for neurotransmitter release via their first C2 (C2A) domain. Here we describe the effect of Mg2+ on phospholipid binding to the C2A domains of multiple synaptotagmins (II-VI), and demonstrate that only synaptotagmin III can bind negatively charged phospholipids [phosphatidylserine (PS) and phosphatidylinositol] in a Mg2+-dependent manner. The Mg2+-dependent interaction with PS was found to have an EC50 of approx. 30 microM Mg2+, which is comparable to that of Sr2+ and Ba2+ (EC50 values of approx. 10 microM). This binding property of the C2A domain is specific to synaptotagmin III, because none of the C2A domains of other proteins, such as rabphilin 3A, Doc2alpha, Doc2beta or Gap1(m), showed phospholipid binding activity in the presence of 1 mM Mg2+. Our results suggest that synaptotagmin III is involved in presynaptic functions different from those of synaptotagmins I and II.
突触结合蛋白是突触小泡的钙离子和磷脂结合蛋白，可能通过其第一个C2（C2A）结构域作为神经递质释放的钙离子受体发挥作用。在此，我们描述了镁离子对多种突触结合蛋白（II-VI）的C2A结构域与磷脂结合的影响，并证明只有突触结合蛋白III能够以镁离子依赖的方式结合带负电荷的磷脂[磷脂酰丝氨酸（PS）和磷脂酰肌醇]。发现与PS的镁离子依赖相互作用的半数有效浓度（EC50）约为30微摩尔镁离子，这与锶离子和钡离子的情况相当（EC50值约为10微摩尔）。C2A结构域的这种结合特性是突触结合蛋白III特有的，因为其他蛋白质（如rabphilin 3A、Doc2α、Doc2β或Gap1（m））的C2A结构域在存在1毫摩尔镁离子的情况下均未显示出磷脂结合活性。我们的结果表明，突触结合蛋白III参与了与突触结合蛋白I和II不同的突触前功能。
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