Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, ON M5S 3H6, Canada.
Biochemistry. 2014 Aug 5;53(30):5008-16. doi: 10.1021/bi500622x. Epub 2014 Jul 16.
The design of new optogenetic tools for controlling protein function would be facilitated by the development of protein scaffolds that undergo large, well-defined structural changes upon exposure to light. Domain swapping, a process in which a structural element of a monomeric protein is replaced by the same element of another copy of the same protein, leads to a well-defined change in protein structure. We observe domain swapping in a variant of the blue light photoreceptor photoactive yellow protein in which a surface loop is replaced by a well-characterized protein-protein interaction motif, the E-helix. In the domain-swapped dimer, the E-helix sequence specifically binds a partner K-helix sequence, whereas in the monomeric form of the protein, the E-helix sequence is unable to fold into a binding-competent conformation and no interaction with the K-helix is seen. Blue light irradiation decreases the extent of domain swapping (from Kd = 10 μM to Kd = 300 μM) and dramatically enhances the rate, from weeks to <1 min. Blue light-induced domain swapping thus provides a novel mechanism for controlling of protein-protein interactions in which light alters both the stability and the kinetic accessibility of binding-competent states.
设计新的光遗传学工具来控制蛋白质功能将得益于蛋白质支架的发展，这些蛋白质支架在暴露于光时会发生大的、明确定义的结构变化。结构域交换是一个单体蛋白质的结构元件被同一蛋白质的另一个副本的相同元件取代的过程，导致蛋白质结构的明确定义变化。我们在蓝光光感受器光活性黄色蛋白的一种变体中观察到结构域交换，其中表面环被一个特征明确的蛋白质-蛋白质相互作用基序，E 螺旋所取代。在结构域交换的二聚体中，E 螺旋序列特异性地结合伴侣 K 螺旋序列，而在蛋白质的单体形式中，E 螺旋序列无法折叠成结合竞争构象，并且没有观察到与 K 螺旋的相互作用。蓝光照射降低了结构域交换的程度（从 Kd = 10 μM 到 Kd = 300 μM），并极大地提高了速率，从数周缩短至 <1 分钟。蓝光诱导的结构域交换因此提供了一种新的机制来控制蛋白质-蛋白质相互作用，其中光改变结合竞争状态的稳定性和动力学可及性。
