Bennett A F, Hayes N V, Baines A J
Biological Laboratory, University of Kent, Canterbury, U.K.
Biochem J. 1991 Jun 15;276 ( Pt 3)(Pt 3):793-9. doi: 10.1042/bj2760793.
Synapsin 1 is one of a family of phosphoproteins located on small synaptic vesicles (SSV) in the presynaptic terminal, and probably plays a critical role in the process of neuronal exocytosis by providing regulated linkages between SSV and the cytoskeleton. Two forms of synapsin 1 are produced from a single gene by differential mRNA splicing: 1a, 706 amino acid residues, and 1b, 670 residues. Synapsin 1 has two structural domains, a globular N-terminal head domain and an elongated tail domain. Electron microscopy of nerve terminals in situ and reconstitution studies in vitro indicates that synapsin 1 can interact with microtubules, microfilaments and brain spectrin. In vitro, synapsin 1 can bundle microtubules. This could either occur by synapsin 1 being at least bivalent for microtubules, or by univalent synapsin 1 molecules aggregating to form complexes that are more than univalent. To resolve this question, we have taken the approach of preparing defined fragments of synapsin 1 from each structural domain and analysing them for tubulin-binding activity. Our results show that there are tubulin-binding sites in both head and tail domains. We conclude that synapsin 1 monomers should be able to cross-link microtubules.
突触素1是位于突触前终末小突触囊泡（SSV）上的一种磷蛋白家族成员，可能通过在SSV和细胞骨架之间提供调控连接，在神经元胞吐过程中发挥关键作用。通过差异mRNA剪接，从单个基因产生两种形式的突触素1：1a，含706个氨基酸残基；1b，含670个残基。突触素1有两个结构域，一个球状的N端头部结构域和一个细长的尾部结构域。对原位神经终末的电子显微镜观察和体外重组研究表明，突触素1可与微管、微丝和脑血影蛋白相互作用。在体外，突触素1可使微管成束。这可能是由于突触素1对微管至少为二价，或者是单价突触素1分子聚集形成多价复合物。为解决这个问题，我们采用了从每个结构域制备突触素1的特定片段并分析其微管蛋白结合活性的方法。我们的结果表明，头部和尾部结构域均存在微管蛋白结合位点。我们得出结论，突触素1单体应该能够交联微管。
