Institutes of Biomedical Sciences, Fudan University, Shanghai, P.R. China.
Mol Cell. 2010 Feb 12;37(3):383-95. doi: 10.1016/j.molcel.2010.01.024.
While most SNAREs are permanently anchored to membranes by their transmembrane domains, the dually lipidated SNARE Ykt6 is found both on intracellular membranes and in the cytosol. The cytosolic Ykt6 is inactive due to the autoinhibition of the SNARE core by its longin domain, although the molecular basis of this inhibition is unknown. Here, we demonstrate that unlipidated Ykt6 adopts multiple conformations, with a small population in the closed state. The structure of Ykt6 in complex with a fatty acid suggests that, upon farnesylation, the Ykt6 SNARE core forms four alpha helices that wrap around the longin domain, forming a dominantly closed conformation. The fatty acid, buried in a hydrophobic groove formed between the longin domain and its SNARE core, is essential for maintaining the autoinhibited conformation of Ykt6. Our study reveals that the posttranslationally attached farnesyl group can actively regulate Ykt6 fusion activity in addition to its anticipated membrane-anchoring role.
虽然大多数 SNARE 蛋白通过其跨膜结构域永久锚定在膜上，但双脂化的 SNARE Ykt6 既存在于细胞内膜上，也存在于细胞质中。由于其长链结构域的自身抑制，细胞质中的 Ykt6 处于无活性状态，尽管这种抑制的分子基础尚不清楚。在这里，我们证明了未脂化的 Ykt6 采用多种构象，其中一小部分处于关闭状态。Ykt6 与脂肪酸复合物的结构表明，在法尼基化后，Ykt6 SNARE 核心形成四个α螺旋，围绕长链结构域缠绕，形成主要的封闭构象。脂肪酸埋藏在长链结构域与其 SNARE 核心之间形成的疏水槽中，对于维持 Ykt6 的自身抑制构象是必不可少的。我们的研究表明，除了预期的膜锚定作用外，翻译后附加的法尼基基团还可以主动调节 Ykt6 的融合活性。
