Abstract
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 language | English (US) |
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Pages (from-to) | 93-96 |
Number of pages | 4 |
Journal | FEBS Letters |
Volume | 516 |
Issue number | 1-3 |
DOIs | |
State | Published - Apr 10 2002 |
Keywords
- C domain
- Calcium binding
- Neurotransmitter release
- Nuclear magnetic resonance
- Relaxation
- Synaptotagmin
ASJC Scopus subject areas
- Biophysics
- Structural Biology
- Biochemistry
- Molecular Biology
- Genetics
- Cell Biology