The permeabilized SecY protein-translocation channel can serve as a nonspecific sugar transporter

Mei, Sen; Xie, Chong; Mi, Hao; Xue, Chuang; Guo, Qiang; Du, Guang-Qing; Li, Guo-Bei; Li, Cai-Xia; Qu, Ya-Nan; Xiong, Ming-Hao; Jiang, Yang; Tan, Tian-Wei; Yang, Shang-Tian; Fan, Li-Hai

As the initial step in carbohydrate catabolism in cells, the substrate-specific transporters via active transport and facilitated diffusion play a decisive role in passage of sugars through the plasma membrane into the cytoplasm. The SecY complex (SecYEG) in bacteria forms a membrane channel responsible for protein translocation. This work demonstrates that weakening the sealability of the SecY channel allowed free diffusion of sugars, including glucose, fructose, mannose, xylose, arabinose, and lactose, into the engineered cells, facilitating its rapid growth on a wide spectrum of monosaccharides and bypassing/reducing stereospecificity, transport saturation, competitive inhibition, and carbon catabolite repression (CCR), which are usually encountered with the specific sugar transporters. The SecY channel is structurally conserved in prokaryotes, thus it may be engineered to serve as a unique and universal transporter for bacteria to passage sugars as demonstrated in Escherichia coli and Clostridium acetobutylicum.