White Susan Roehl, Evans Katia J, Lary Jeffrey, Cole James L, Lauring Brett
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
J Cell Biol. 2007 Mar 26;176(7):995-1005. doi: 10.1083/jcb.200610072.
Spastin, an AAA ATPase mutated in the neurodegenerative disease hereditary spastic paraplegia, severs microtubules. Many other AAA proteins form ring-shaped hexamers and contain pore loops, which project into the ring's central cavity and act as ratchets that pull on target proteins, leading, in some cases, to conformational changes. We show that Spastin assembles into a hexamer and that loops within the central pore recognize C-terminal amino acids of tubulin. Key pore loop amino acids are required for severing, including one altered by a disease-associated mutation. We also show that Spastin contains a second microtubule binding domain that makes a distinct interaction with microtubules and is required for severing. Given that Spastin engages the MT in two places and that both interactions are required for severing, we propose that severing occurs by forces exerted on the C-terminal tail of tubulin, which results in a conformational change in tubulin, which releases it from the polymer.
痉挛素是一种在神经退行性疾病遗传性痉挛性截瘫中发生突变的AAA型ATP酶，它能切断微管。许多其他AAA蛋白形成环状六聚体并含有孔环，孔环伸入环的中心腔并充当拉动靶蛋白的棘轮，在某些情况下会导致构象变化。我们发现痉挛素组装成六聚体，并且中心孔内的环识别微管蛋白的C末端氨基酸。切断微管需要关键的孔环氨基酸，包括一个因疾病相关突变而改变的氨基酸。我们还发现痉挛素含有第二个微管结合结构域，该结构域与微管有独特的相互作用，并且是切断微管所必需的。鉴于痉挛素在两个位置与微管结合，并且这两种相互作用都是切断微管所必需的，我们提出切断是通过对微管蛋白C末端尾巴施加力来实现的，这会导致微管蛋白发生构象变化，从而使其从聚合物中释放出来。
