Aleksandrov A A, Riordan J R
Mayo Foundation, Mayo Clinic, Scottsdale, AZ 85259, USA.
FEBS Lett. 1998 Jul 10;431(1):97-101. doi: 10.1016/s0014-5793(98)00713-3.
Single channel currents of wild-type CFTR reconstituted in lipid bilayers were recorded to study the temperature dependence of channel gating between +20 degrees C and +40 degrees C. The opening of the channel was highly temperature dependent and required an activation energy of about 100 kJ/mol. Closing of the channel was only weakly temperature dependent with an activation energy close to that of diffusion in water. We found no significant difference in the free energy between the open and closed states. Most of the excess energy needed to activate channel opening is used to diminish the entropy of the open state. This structural reorganization is initiated by ATP binding followed by interconversion to the open channel structure as the CFTR-ATP-Mg complex passes to the transition state for hydrolysis. The energy of the CFTR-ATP-Mg interaction in the transition state is responsible for the CFTR ion channel opening rather than the energy of ATP hydrolysis. Channel closing is a diffusion limited process and does not require additional ATP binding.
为研究野生型囊性纤维化跨膜传导调节因子（CFTR）在脂质双分子层中重构后的单通道电流在20摄氏度至40摄氏度之间通道门控的温度依赖性，进行了相关记录。通道的开放高度依赖温度，且需要约100千焦/摩尔的活化能。通道的关闭仅对温度有微弱依赖性，其活化能接近水中扩散的活化能。我们发现开放态和关闭态之间的自由能没有显著差异。激活通道开放所需的大部分多余能量用于降低开放态的熵。这种结构重组由ATP结合引发，随后随着CFTR - ATP - Mg复合物进入水解的过渡态，转变为开放通道结构。过渡态中CFTR - ATP - Mg相互作用的能量负责CFTR离子通道的开放，而非ATP水解的能量。通道关闭是一个扩散限制过程，不需要额外的ATP结合。
