Role of Glycosphingolipid Conformational Change in Membrane Pore Forming Activity of Cobra Cardiotoxin

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• 作者：Siu-Cin Tjong ; Po-Long Wu ; Chang-Mao Wang ; Wei-Ning Huang ; Nan-Lu Ho ; Wen-guey Wu
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：October 30, 2007
• 年：2007
• 卷：46
• 期：43
• 页码：12111 - 12123
• 全文大小：699K
• 年卷期：v.46,no.43(October 30, 2007)
• ISSN：1520-4995

文摘

The major cardiotoxin from Taiwan cobra (CTX A3) is a pore forming -sheet polypeptidethat requires sulfatide (sulfogalactosylceramide, SGC) on the plasma membrane of cardiomyocytes forCTX-induced membrane leakage and cell internalization. Herein, we demonstrate by fluorescencespectroscopic studies that sulfatides induce CTX A3 oligomerization in sulfatide containing phosphatidylcholine (PC) vesicles to form transient pores with pore size and lifetime in the range of about 30 Åand 10^-2 s, respectively. These values are consistent with the CTX A3-induced conductance and meanlifetime determined previously by using patch-clamp electrophysiological experiments on the plasmamembrane of H9C2 cells. We also derived the peripheral binding structural model of CTX A3-sulfatidecomplex in sulfatide containing PC micelles by NMR and molecular docking method and compared withother CTX A3-sulfatide complex structure determined previously by X-ray in membrane-like environment.The NMR results indicate that sulfatide head group conformation changes from a bent shovel (-sc/ap)to an extended (sc/ap) conformation upon initial binding of CTX A3. An additional global reorientationof sulfatide molecule is also needed for CTX A3 dimer formation as inferred by the difference betweenthe X-ray and NMR complex structure. Since the overall folding of CTX A3 molecules remained thesame, sulfatide in phospholipid bilayer is proposed to play an active role by involving its local and globalconformational changes to promote both the oligomerization and reorientation of CTX A3 molecule forits transient pore formation and cell internalization.