Science Advances, 23 October, 2020, DOI：https://doi.org/10.1126/sciadv.abd7182
Discovery and mechanism of a pH-dependent dual-binding-site switch in the interaction of a pair of protein modules
Xingzhe Yao*, Chao Chen*, Yefei Wang*, Sheng Dong, Ya-Jun Liu, Yifei Li, Zhenling Cui, Weibin Gong, Sarah Perrett, Lishan Yao, Raphael Lamed, Edward A. Bayer, Qiu Cui and Yingang Feng
Many important proteins undergo pH-dependent conformational changes resulting in “on-off” switches for protein function, which are essential for regulation of life processes and have wide application potential. Here, we report a pair of cellulosomal assembly modules, comprising a cohesin and a dockerin from Clostridium acetobutylicum, which interact together following a unique pH-dependent switch between two functional sites rather than on-off states. The two cohesin-binding sites on the dockerin are switched from one to the other at pH 4.8 and 7.5 with a 180° rotation of the bound dockerin. Combined analysis by nuclear magnetic resonance spectroscopy, crystal structure determination, mutagenesis, and isothermal titration calorimetry elucidates the chemical and structural mechanism of the pH-dependent switching of the binding sites. The pH-dependent dual-binding-site switch not only represents an elegant example of biological regulation but also provides a new approach for developing pH-dependent protein devices and biomaterials beyond an on-off switch for biotechnological applications.