Lai, Ying Shin, Yeon-Kyun 2024-01-20T15:02:32Z 2024-01-20T15:02:32Z 2021-09-05 2012-04-01 0264-6021 https://pubs.kist.re.kr/handle/201004/129344 Syt1 (synaptotagmin 1) is a major Ca2+ sensor for synaptic vesicle fusion. Although. Syt1 is known to bind, to SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor) complexes and to the membrane, the mechanism by which Syt1 regulates vesicle fusion is controversial. In the present study we used in vitro lipid-mixing assays to investigate the Ca2+-dependent Syt1 function in proteoliposome fusion. To study the role of acidic lipids, the concentration of negatively charged DOPS (1,2-dioleoyl-sn-glycero-3-phospho-L-serine) in the vesicle was varied. Syt1 stimulated lipid mixing by 3-10-fold without Ca2+. However, with Ca2+ there was an additional 2-5-fold enhancement. This Ca2+-dependent stimulation was observed only when there was excess PS (phosphatidylserine) on the t-SNARE (target SNARE) side. If there was equal or more PS on the v-SNARE (vesicule SNARE) side the Ca2+ dependent stimulation was not observed. We found that Ca2+ at a concentration between 10 and 50 mu M was sufficient to give rise to the maximal enhancement. The single-vesicle-fusion assay indicates that the Ca2+-dependent enhancement was mainly on docking, whereas its effect on lipid mixing was small. Thus for Syt1 to function as a Ca2+ sensor, a charge asymmetry appears to be important and this may play a role in steering Syt1 to productively trans bind to the plasma membrane. English PORTLAND PRESS LTD SYNAPTIC SNARE COMPLEX MEMBRANE-FUSION 3-DIMENSIONAL STRUCTURE SINGLE-MOLECULE I FUNCTIONS CALCIUM BINDING MECHANISM EXOCYTOSIS AFFINITY The importance of an asymmetric distribution of acidic lipids for synaptotagmin 1 function as a Ca2+ sensor Article 10.1042/BJ20112044 1 BIOCHEMICAL JOURNAL, v.443, pp.223 - 229 BIOCHEMICAL JOURNAL 443 223 229 scie scopus 000302590500024 2-s2.0-84858328639 Biochemistry & Molecular Biology Biochemistry & Molecular Biology Article SYNAPTIC SNARE COMPLEX MEMBRANE-FUSION 3-DIMENSIONAL STRUCTURE SINGLE-MOLECULE I FUNCTIONS CALCIUM BINDING MECHANISM EXOCYTOSIS AFFINITY charge asymmetry 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor (SNARE) synaptotagmin 1 vesicle fusion