Department of Physics and Astronomy, Rice University, Houston, Texas, USA.
Biophys J. 2012 Jan 4;102(1):48-55. doi: 10.1016/j.bpj.2011.11.4009. Epub 2012 Jan 3.
The force model of protein-mediated membrane fusion hypothesizes that fusion is driven by mechanical forces exerted on the membranes, but many details are unknown. Here, we investigated by x-ray diffraction the consequence of applying compressive force on a stack of membranes against the hydration barrier. We found that as the osmotic pressure increased, the lamellar phase transformed first to a new phase of tetragonal lattice (T-phase) over a narrow range of relative humidity, and then to a phase of rhombohedral lattice. The unit cell structure changed from parallel bilayers to a bent configuration with a point contact between adjacent bilayers and then to the stalk hemifusion configuration. The T-phase is discussed as a possible transition state in the membrane merging pathway of fusion. We estimate the work required to form the T-phase and the subsequent hemifusion-stalk-resembling R-phase. The work for the formation of a stalk is compatible with the energy estimated to be released by several SNARE complexes.
蛋白质介导的膜融合的力模型假设融合是由施加在膜上的机械力驱动的，但许多细节尚不清楚。在这里，我们通过 X 射线衍射研究了在水合势障碍下对堆叠膜施加压缩力的后果。我们发现，随着渗透压的增加，层状相首先在相对湿度较窄的范围内转变为新的四方晶格（T 相），然后转变为菱形晶格。单元结构从平行双层变为相邻双层之间的点接触的弯曲构型，然后变为茎半融合构型。T 相被认为是融合过程中膜融合途径的可能过渡态。我们估计形成 T 相和随后的半融合-茎类似的 R 相所需的功。形成茎所需的功与通过几个 SNARE 复合物估计释放的能量相兼容。
