Orientation of the Dysferlin C2A Domain is Responsive to the Composition of Lipid Membranes
Orientation of the Dysferlin C2A Domain is Responsive to the Composition of Lipid Membranes
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DOI：
10.1021/acs.jpcb.2c06716
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发表时间：
2023-01-06
影响因子：
3.3
通讯作者：
Baio，Joe E.
中科院分区：
文献类型：
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作者：
Carpenter，Andrew P.;Khuu，Patricia;Baio，Joe E.
Dysferlin是一种230 kD的蛋白质，其通过募集囊泡以经由囊泡融合修补损伤部位，在肌肉肌膜的微米大小损伤的主动再密封中发挥关键功能。当突变破坏这种修复过程或dysferlin不存在时，在人类中观察到肌肉营养不良。虽然dysferlin的C2 A结构域（dysC 2A）的脂质结合被认为是膜重新密封过程的基础，但这种相互作用的分子机制尚未完全了解。通过应用非线性表面特异性振动光谱，我们已经成功地证明了dysferlin的N-末端C2 A结构域（dysC 2A）改变其结合方向，响应于膜的脂质组成。这些实验表明，dysC 2A利用一般的静电结合相互作用来结合大多数阴离子脂质表面，将其钙结合环插入脂质表面，同时使其β-折叠与表面法线成30-40°。然而，在存在PI（4，5）P2的脂质表面，dysC 2A使其β-折叠从表面法线倾斜超过60°以暴露多元面，同时其结合到PI（4，5）P2表面。这两种脂质结合机制都显示出与dysC 2A诱导的脂质聚集一起发生。这些不同的结合机制表明，dysC 2A可以提供一个分子线索，以更大的dysferlin蛋白的信号是否结合到肌膜或其他脂质表面。
Dysferlin is a 230 kD protein that plays a critical function in the active resealing of micron-sized injuries to the muscle sarcolemma by recruiting vesicles to patch the injured site via vesicle fusion. Muscular dystrophy is observed in humans when mutations disrupt this repair process or dysferlin is absent. While lipid binding by dysferlin’s C2A domain (dysC2A) is considered fundamental to the membrane resealing process, the molecular mechanism of this interaction is not fully understood. By applying nonlinear surface-specific vibrational spectroscopy, we have successfully demonstrated that dysferlin’s N-terminal C2A domain (dysC2A) alters its binding orientation in response to a membrane’s lipid composition. These experiments reveal that dysC2A utilizes a generic electrostatic binding interaction to bind to most anionic lipid surfaces, inserting its calcium binding loops into the lipid surface while orienting its β-sheets 30–40° from surface normal. However, at lipid surfaces, where PI(4,5)P2 is present, dysC2A tilts its β-sheets more than 60° from surface normal to expose a polybasic face, while it binds to the PI(4,5)P2 surface. Both lipid binding mechanisms are shown to occur alongside dysC2A-induced lipid clustering. These different binding mechanisms suggest that dysC2A could provide a molecular cue to the larger dysferlin protein as to signal whether it is bound to the sarcolemma or another lipid surface.