Journal
FEBS LETTERS
Volume 516, Issue 1-3, Pages 93-96Publisher
WILEY
DOI: 10.1016/S0014-5793(02)02508-5
Keywords
neurotransmitter release; synaptotagmin; C-2 domain; calcium binding; relaxation; nuclear magnetic resonance
Funding
- NINDS NIH HHS [NS40944] Funding Source: Medline
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The off rate from the first calcium-binding site of the C(2)A domain of synaptotagmin 1, a putative calcium receptor in neurotransmitter release, has been determined by N-15-nuclear magnetic resonance relaxation dispersion measurements. The exchange rate was obtained by fitting the dependence of the transverse relaxation rates on the interval between 180degrees pulses in relaxation-compensated CPMG experiments at 3.2 muM calcium concentration. The measured k(ex) is 2.0 X 10(3) s(-1). The calcium on rate of 3.5 +/- 1 X 10(7) s(-1), determined from the measured off rate and the dissociation constant (5.3 X 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. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.
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