Abstract
It has recently been shown that sulfatide plays an important role in pore-forming process of CTX A3 on cell membrane. In order to understand the details of CTX – sulfatide interaction, we employed intrinsic fluorescence and isothermal titration calorimeter (ITC) to study the binding mode of CTX A3 and A5 to micelles containing sulfatide. We also applied nuclear magnetic resonance to investigate the possible binding CTX site of galactose derivative(the sulfogalactoyl headgroup moiety of sulfatide). Our results suggest that the binding mode of CTX A3 with sulfatide and its headgroup mimetics is different from that of CTX A5. Specifically,sulfatide headgroup and its derivative binds to CTX A3 at the core region whereas that binds to CTX A5 near loop I region. The different mode of sulfatide interaction with CTX A3 and CTX A5 provides an explanation on why CTX A5 could not form pore in cell membranes.