Myo1c binds tightly and specifically to phosphatidylinositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate
Myo1c binds tightly and specifically to phosphatidylinositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate
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DOI：
10.1073/pnas.0505685103
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发表时间：
2006-02-28
影响因子：
11.1
通讯作者：
Ostap, EM
中科院分区：
文献类型：
--
作者：
Hokanson, DE;Ostap, EM
肌球蛋白-I是肌球蛋白超家族中的单头成员，通过其碱性尾部结构域与酸性磷脂结合。膜结合对于肌球蛋白-I的正确定位和功能是必不可少的。然而，关于肌球蛋白-I与磷脂的直接联系或磷脂头基结合的特异性的生理学相关性知之甚少。为了更好地了解肌球蛋白-L-膜结合的机制，我们测量了一个重组的myo1c尾部结构(包括三个IQ结构域和结合的钙调蛋白)与由磷脂酰胆碱和不同浓度的磷脂酰丝氨酸(PS)或磷脂酰肌醇4，5-二磷酸(PIP2)组成的大单层囊泡(LuV)结合的有效解离常数。我们发现，myo1c-Tail与含有60%PS的LuV紧密结合，但与含有生理PS浓度(<；40%)的LuV结合很弱。Myo1c尾部而不是IQ基序与含有2%PIP2的LuV紧密结合。此外，我们还发现，在狼疮中，myo1c尾部与可溶性的三磷酸肌醇结合的亲和力与PIP2几乎相同，这表明myolc与PIP2的头部是特异结合的。我们还发现，在上皮细胞中表达的GFP-肌球蛋白-1尾嵌合体瞬时定位于已知富含PIP2的区域。我们的结果表明，myolc不与生理浓度的PS结合，而是与PIP2紧密结合。
Myosin-I is the single-headed member of the myosin superfamily that associates with acidic phospholipids through its basic tail domain. Membrane association is essential for proper myosin-I localization and function. However, little is known about the physiological relevance of the direct association of myosin-I with phospholipids or about phospholipid headgroup-binding specificity. To better understand the mechanism of myosin-l-membrane association, we measured effective dissociation constants for the binding of a recombinant myo1c tail construct (which includes three IQ domains and bound calmodulins) to large unilamellar vesicles (LUVs) composed of phosphatidylcholine and various concentrations of phosphatidylserine (PS) or phosphatidylinositol 4,5-bisphosphate (PIP2). We found that the myo1c-tail binds tightly to LUVs containing > 60% PS but very weakly to LUVs containing physiological PS concentrations (< 40%). The myo1c tail and not the IQ motifs bind tightly to LUVs containing 2% PIP2. Additionally, we found that the myo1c tail binds to soluble inositol-1,4,5-trisphosphate with nearly the same affinity as to PIP2 in LUVs, suggesting that myolc binds specifically to the headgroup of PIP2. We also show that a GFP-myosin-1-tail chimera expressed in epithelial cells is transiently localized to regions known to be enriched in PIP2. Our results suggest that myolc does not bind to physiological concentrations of PS but rather binds tightly to PIP2.