NMR measurement of the off rate from the first calcium-binding site of the synaptotagmin I C2A domain

Oscar Millet, Pau Bernadó, Jesús Garcia, Jose Rizo-Rey, Miquel Pons

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22 Scopus citations


The off rate from the first calcium-binding site of the C2A domain of synaptotagmin I, a putative calcium receptor in neurotransmitter release, has been determined by 15N-nuclear magnetic resonance relaxation dispersion measurements. The exchange rate was obtained by fitting the dependence of the transverse relaxation rates on the interval between 180° pulses in relaxation-compensated CPMG experiments at 3.2 μM calcium concentration. The measured kex is 2.0×103 s-1. The calcium on rate of 3.5±1×107 s-1, determined from the measured off rate and the dissociation constant (5.3×10-5 M), is close to the diffusion limit. These results are consistent with the proposed role of synaptotagmin I as a calcium sensor in release, but suggest that additional factors may help to accelerate the diffusion of Ca2+ to the sensor.

Original languageEnglish (US)
Pages (from-to)93-96
Number of pages4
JournalFEBS Letters
Issue number1-3
StatePublished - Apr 10 2002



  • C domain
  • Calcium binding
  • Neurotransmitter release
  • Nuclear magnetic resonance
  • Relaxation
  • Synaptotagmin

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

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