Background

Syntaxin-1A and Sso1 are syntaxin family SNARE proteins engaged in synaptic vesicle fusion and yeast exocytosis. The syntaxin-1A SNARE motif can form a fusogenic SNARE complex with Sso1 partners. However, a chimera in which the SNARE motif in syntaxin-1A is introduced into Sso1 was not functional in yeast because the chimera is retained in the ER. Through the analysis of the transport defect of Sso1/syntaxin-1A chimeric SNAREs, we found that their SNARE motifs have distinctive properties.

Methods

Sso1, syntaxin-1A, and Sso1/syntaxin-1A chimeric SNAREs were expressed in yeast cells and their localization and interaction with other SNAREs are analyzed.

Results

SNARE proteins containing the syntaxin-1A SNARE motif exhibit a transport defect because they form a cis-SNARE complex in the ER. Ectopic SNARE complex formation can be prevented in syntaxin-1A by binding to a Sec1/Munc-18-like (SM) protein. In contrast, the SNARE motif of Sso1 does not form an ectopic SNARE complex. Additionally, we found that the SNARE motif in syntaxin-1A, but not that in Sso1, self-interacts, even when it is in the inactive form and bound to the SM protein.

Conclusions

The SNARE motif in syntaxin-1A, but not in Sso1, likely forms ectopic SNARE complex. Because of this property, the SM protein is necessary for syntaxin-1A to prevent its promiscuous assembly and to promote its export from the ER.

General significance

Properties of SNARE motifs affect characteristics of SNARE proteins. The regulatory mechanisms of SNARE proteins are, in part, designed to handle such properties.

中文翻译：

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SNARE蛋白质的特征由SNARE主题的独特属性定义。

背景

Syntaxin-1A和Sso1是Syntaxin家族的SNARE蛋白，参与突触小泡融合和酵母胞吐作用。Syntaxin-1A SNARE基序可以与Sso1伙伴形成融合的SNARE复合体。然而，将语法素-1A中的SNARE基序引入Sso1的嵌合体在酵母中不起作用，因为该嵌合体保留在ER中。通过分析Sso1 / syntaxin-1A嵌合snare的运输缺陷，我们发现它们的snare基序具有独特的属性。

方法

Sso1，syntaxin-1A和Sso1 / syntaxin-1A嵌合SNARE在酵母细胞中表达，并分析了它们的定位和与其他SNARE的相互作用。

结果

包含syntaxin-1A SNARE基序的SNARE蛋白表现出运输缺陷，因为它们在ER中形成顺式-SNARE复合物。通过与Sec1 / Munc-18-like（SM）蛋白结合，可以防止Syntaxin-1A中异位SNARE复合物的形成。相反，Sso1的SNARE基序不形成异位SNARE复合体。此外，我们发现，syntaxin-1A中的SNARE主题（而不是Sso1中的）却相互影响，即使它处于非活性形式并与SM蛋白结合也是如此。

结论

syntaxin-1A中的SNARE主题（而不是Sso1中的）可能形成异位SNARE复合体。由于此特性，syntaxin-1A必需使用SM蛋白来防止其混杂组装并促进其从ER出口。

一般意义

SNARE基序的特性会影响SNARE蛋白质的特性。SNARE蛋白的调节机制在某种程度上被设计来处理这些特性。