Mechanism of the Calcium-dependent Multimerization of Synaptotagmin VII Mediated by Its First and Second C2 Domains

Mitsunori Fukuda, Katsuhiko Mikoshiba

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26 Citations (Scopus)


The Ca2+-dependent oligomerization activity of the second C2 (C2B) domain of synaptotagmin I (Syt I) has been hypothesized to regulate neurotransmitter release. We previously showed that the cytoplasmic domains of several other Syt isoforms also show Ca2+-dependent oligomerization activity (Fukuda, M., and Mikoshiba, K. (2000) J. Biol. Chem. 275, 28180-28185), but little is known about the involvement of their C2 domains in Ca 2+-dependent oligomerization. In this study, we analyzed the Ca 2+-dependent oligomerization properties of the first (C2A) and the second C2 (C2B) domains of Syt VII. Unlike Syt I, both C2 domains of Syt VII contribute to Ca2+-dependent homo- and hetero-oligomerization with other isoforms. For instance, the Syt VII C2A domain Ca 2+-dependently binds itself and the C2A domain of Syt VI but not its C2B domain, whereas the Syt VII C2B domain Ca2+-dependently binds itself and the C2B domain of Syt II but not its C2A domain. In addition, we showed by gel filtration that a single Syt VII C2 domain is sufficient to form a Ca2+-dependent multimer of very high molecular weight. Because of this "two handed" structure, the Syt VII cytoplasmic domain has been found to show the strongest Ca2+-dependent multimerization activity in the Syt family. We also identified Asn-328 in the C2B domain as a crucial residue for the efficient Ca2+-dependent switch for multimerization by site-directed mutagenesis. Our results suggest that Syt VII is a specific isoform that can cluster different Syt isoforms with two hands in response to Ca2+.

Original languageEnglish
Pages (from-to)27670-27676
Number of pages7
JournalJournal of Biological Chemistry
Issue number29
Publication statusPublished - 2001 Jul 20


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