N-terminal SNARE complex binding domain of the complexin family of SNARE regulators; Complexins (CPXs) are small, cytosolic proteins that bind to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex to regulate synaptic vesicle exocytosis. There are four CPX isoforms: complexin I/synaphin-2, complexin II/synaphin-1, complexin III and complexin IV. CPXs I and II are highly homologous hydrophilic proteins that are enriched in neurons where they colocalize with syntaxin and SNAP25. They regulate the sequential interactions of alpha-SNAP and synaptotagmins with the SNAP receptor during exocytosis. CPXs III and IV are the only CPX isoforms present in retinal ribbon synapses. In addition, CPXs III and IV carry an extension with a functional CAAX-box farnesylation site that is absent in CPXs I and II. Their C-terminal farnesylation regulates their synaptic targeting and modulatory function in transmitter release. They may contribute to the unique release efficacy of retinal sensory neurons. CPXs III and IV can functionally replace CPXs I and II. Most of the invertebrate CPXs are more similar to CPXs I and II than to CPXs III and IV. This model corresponds to the N-terminal region of CPX that is responsible for SNARE complex binding.

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gi 1838099101  64 FKSYNEDLEKERQQREAMNAQKNAERATMRAQFRNKYQLSES 105
Cdd:cd22809     3 EEEYQKQLEEEKKERDAAFAQKKAERAAMRAHLREKYRLPKN 44

N-terminal SNARE complex binding domain found in complexins III and IV; Complexins (CPXs) are small, cytosolic proteins that bind to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex to regulate synaptic vesicle exocytosis. Complexins III (CPX III) and IV (CPX IV) are the only CPX isoforms present in retinal ribbon synapses. They carry an extension with a functional CAAX-box farnesylation site that is absent in CPXs I and II. Their C-terminal farnesylation regulates their synaptic targeting and modulatory function in transmitter release. They may contribute to the unique release efficacy of retinal sensory neurons. CPXs III and IV can functionally replace CPXs I and II, which regulate a late step in the release process, most likely by stabilizing SNARE complexes and thus maintaining synaptic vesicles in a highly release competent state. This model corresponds to the N-terminal SNARE complex binding domain of CPXs III and IV.

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gi 1838099101  64 FKSYNEDLEKERQQREAMNAQKNAERATMRAQFRNKYQLSES 105
Cdd:cd22809     3 EEEYQKQLEEEKKERDAAFAQKKAERAAMRAHLREKYRLPKN 44

N-terminal SNARE complex binding domain found in complexins III and IV; Complexins (CPXs) are small, cytosolic proteins that bind to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex to regulate synaptic vesicle exocytosis. Complexins III (CPX III) and IV (CPX IV) are the only CPX isoforms present in retinal ribbon synapses. They carry an extension with a functional CAAX-box farnesylation site that is absent in CPXs I and II. Their C-terminal farnesylation regulates their synaptic targeting and modulatory function in transmitter release. They may contribute to the unique release efficacy of retinal sensory neurons. CPXs III and IV can functionally replace CPXs I and II, which regulate a late step in the release process, most likely by stabilizing SNARE complexes and thus maintaining synaptic vesicles in a highly release competent state. This model corresponds to the N-terminal SNARE complex binding domain of CPXs III and IV.

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                  ....*....|....*....|....*....|....*....|..
gi 1838099101  64 FKSYNEDLEKERQQREAMNAQKNAERATMRAQFRNKYQLSES 105
Cdd:cd22809     3 EEEYQKQLEEEKKERDAAFAQKKAERAAMRAHLREKYRLPKN 44

Synaphin protein; This family consists of several eukaryotic synaphin 1 and 2 proteins. Synaphin/complexin is a cytosolic protein that preferentially binds to syntaxin within the SNARE complex. Synaphin promotes SNAREs to form precomplexes that oligomerise into higher order structures. A peptide from the central, syntaxin binding domain of synaphin competitively inhibits these two proteins from interacting and prevents SNARE complexes from oligomerising. It is thought that oligomerization of SNARE complexes into a higher order structure creates a SNARE scaffold for efficient, regulated fusion of synaptic vesicles. Synaphin promotes neuronal exocytosis by promoting interaction between the complementary syntaxin and synaptobrevin transmembrane regions that reside in opposing membranes prior to fusion.

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gi 1838099101  64 FKSYNEDLEKERQQREAMNAQKNAERATMRAQFRNKYQLSESRKD---------TNRLRSVGAKVSLPHELSKIIHPEN 133
Cdd:pfam05835  38 EEEYQEALREEEEERKAKHRKMEAEREKMRQHIRDKYRLKKKEEDeaeiqaamePSTEGRLGRDKKTPEELAKMVEEDE 116