Dulubova I, Yamaguchi T, Wang Y, Südhof T C, Rizo J
Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, USA.
Nat Struct Biol. 2001 Mar;8(3):258-64. doi: 10.1038/85012.
Syntaxins and Sec1/munc18 proteins are central to intracellular membrane fusion. All syntaxins comprise a variable N-terminal region, a conserved SNARE motif that is critical for SNARE complex formation, and a transmembrane region. The N-terminal region of neuronal syntaxin 1A contains a three-helix domain that folds back onto the SNARE motif forming a 'closed' conformation; this conformation is required for munc18-1 binding. We have examined the generality of the structural properties of syntaxins by NMR analysis of Vam3p, a yeast syntaxin essential for vacuolar fusion. Surprisingly, Vam3p also has an N-terminal three-helical domain despite lacking apparent sequence homology with syntaxin 1A in this region. However, Vam3p does not form a closed conformation and its N-terminal domain is not required for binding to the Sec1/munc18 protein Vps33p, suggesting that critical distinctions exist in the mechanisms used by syntaxins to govern different types of membrane fusion.
Syntaxin蛋白和Sec1/munc18蛋白是细胞内膜融合的核心。所有Syntaxin蛋白都包含一个可变的N端区域、一个对SNARE复合体形成至关重要的保守SNARE基序以及一个跨膜区域。神经元Syntaxin 1A的N端区域包含一个三螺旋结构域，该结构域向后折叠到SNARE基序上，形成一种“封闭”构象；这种构象是munc18-1结合所必需的。我们通过对Vam3p（一种对液泡融合至关重要的酵母Syntaxin蛋白）进行核磁共振分析，研究了Syntaxin蛋白结构特性的普遍性。令人惊讶的是，尽管Vam3p在该区域与Syntaxin 1A缺乏明显的序列同源性，但它也有一个N端三螺旋结构域。然而，Vam3p不会形成封闭构象，并且其N端结构域对于与Sec1/munc18蛋白Vps33p的结合并非必需，这表明Syntaxin蛋白用于控制不同类型膜融合的机制存在关键差异。
