Unexpected Ca2+-binding properties of synaptotagmin 9

Ok Ho Shin, Anton Maximov, Byung Kook Lim, Josep Rizo, Thomas C. Südhof

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Synaptotagmin 1 (Syt 1) functions as an essential Ca2+ sensor for the fast but not slow component of Ca2+-triggered exocytosis. One hypothesis to account for this selective function, based on the close homology of Syt 1 with synaptotagmin 9 (Syt 9), is that these Syts are redundant for the slow but not the fast component of release. We now show, however, that Syt 9 has unique properties that set it apart from Syt 1. Different from Syt 1, endogenous Syt 9 does not associate Ca2+ dependently or independently with soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) protein complexes, and the Syt 9 C 2B domain does not form Ca2+/phospholipid complexes, whereas such complexes are essential for Syt 1 function. Nevertheless, the C2A domain of Syt 9 functions as a Ca2+-binding module, suggesting that Syts 1 and 9 are Ca2+ sensors with similar Ca 2+-binding sequences but distinct properties that indicate nonoverlapping functions.

Original languageEnglish (US)
Pages (from-to)2554-2559
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Feb 22 2004
Externally publishedYes


  • C domain
  • Exocytosis
  • Membrane fusion
  • Neurotransmitter release
  • Synaptic plasticity

ASJC Scopus subject areas

  • General


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