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

FEBS Letters

Millet, Oscar²  Bernadó, Pau²  Pons, Miquel²  Garcia, Jesús¹  Rizo, Josep¹ 

[1] Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9038, USA;Departament de Quı́mica Orgànica, Universitat de Barcelona, Martı́ i Franquès 1–11, 08028 Barcelona, Spain

关键词: Neurotransmitter release;    Synaptotagmin;    C2 domain;    Calcium binding;    Relaxation;    Nuclear magnetic resonance;   

DOI  :  10.1016/S0014-5793(02)02508-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 k _ex 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.

【 授权许可】

Unknown