Taking Control over Control: Use of Product Sensing in Single Cells to Remove Flux Control at Key Enzymes in Biosynthesis Pathways

• Published in: ACS synthetic biology Vol. 3; no. 1; pp. 21 - 29
• Main Authors: Schendzielorz, Georg, Dippong, Martin, Grünberger, Alexander, Kohlheyer, Dietrich, Yoshida, Ayako, Binder, Stephan, Nishiyama, Chiharu, Nishiyama, Makoto, Bott, Michael, Eggeling, Lothar
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.01.2014
• Subjects: Amino Acid Substitution; Arginine - chemistry; Arginine - metabolism; Aspartate Kinase - genetics; Aspartate Kinase - metabolism; ATP Phosphoribosyltransferase - genetics; ATP Phosphoribosyltransferase - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Corynebacterium glutamicum - enzymology; Corynebacterium glutamicum - metabolism; Flow Cytometry; Histidine - chemistry; Histidine - metabolism; Kinetics; Lysine - chemistry; Lysine - metabolism; Phosphotransferases (Carboxyl Group Acceptor) - chemistry; Phosphotransferases (Carboxyl Group Acceptor) - genetics; Phosphotransferases (Carboxyl Group Acceptor) - metabolism; Plasmids - genetics; Plasmids - metabolism; flux control; allosteric enzymes; fluorescence-activated cell sorting (FACS); metabolite sensor; library screening; single-cell analysis; product sensing
• ISSN: 2161-5063; 2161-5063
• DOI: 10.1021/sb400059y

Enzymes initiating the biosynthesis of cellular building blocks are frequently inhibited by the end-product of the respective pathway. Here we present an approach to rapidly generate sets of enzymes overriding this control. It is based on the in vivo detection of the desired end-product in single cells using a genetically encoded sensor. The sensor transmits intracellular product concentrations into a graded optical output, thus enabling ultrahigh-throughput screens by FACS. We randomly mutagenized plasmid-encoded ArgB of Corynebacterium glutamicum and screened the library in a strain carrying the sensor pSenLys-Spc, which detects l-lysine, l-arginine and l-histidine. Six of the resulting N-acetyl-l-glutamate kinase proteins were further developed and characterized and found to be at least 20-fold less sensitive toward l-arginine inhibition than the wild-type enzyme. Overexpression of the mutein ArgB-K47H-V65A in C. glutamicumΔargR led to the accumulation of 34 mM l-arginine in the culture medium. We also screened mutant libraries of lysC-encoded aspartate kinase and hisG-encoded ATP phosphoribosyltransferase. We isolated 11 LysC muteins, enabling up to 45 mM l-lysine accumulation, and 13 HisG muteins, enabling up to 17 mM l-histidine accumulation. These results demonstrate that in vivo screening of enzyme libraries by using metabolite sensors is extremely well suited to identify high-performance muteins required for overproduction.