A sensitive and specific genetically-encoded potassium ion biosensor for in vivo applications across the tree of life
Sheng-Yi Wu, Yurong Wen, Nelson BC Serre, Cathrine Charlotte Heiede Laursen, Andrea Dietz, Brian Taylor, Mikhail Drobizhev, Rosana S. Molina, Abhi Aggarwal, Vladimir Rančić, Michael E. Becker, Klaus Ballanyi, Kaspar Podgorski, Hajime Hirase, Maiken Nedergaard, Matyáš Fendrych, M. Joanne Lemieux, Daniel F. Eberl, Alan R. Kay, Robert E. Campbell, Yi Shen
Abstract
Potassium ion (K+) plays a critical role as an essential electrolyte in all biological systems. Genetically-encoded fluorescent K+ biosensors are promising tools to further improve our understanding of K+-dependent processes under normal and pathological conditions. Here, we report the crystal structure of a previously reported genetically-encoded fluorescent K+ biosensor, GINKO1, in the K+-bound state. Using structure-guided optimization and directed evolution, we have engineered an improved K+ biosensor, designated GINKO2, with higher sensitivity and specificity. We have demonstrated the utility of GINKO2 for in vivo detection and imaging of K+ dynamics in multiple model organisms, including bacteria, plants, and mice.