A simple, counter-intuitive method for improving the yield of isotope-labeled protein expression in flask-culturedEscherichia coli

NMR is a powerful tool for the structural and dynamic study of proteins. One of the necessary conditions for the study of these proteins is their isotopic labeling with 13 C, 15 N and sometimes 2 H. One of the most widely used methods to obtain these labeled proteins is heterologous expression of the proteins in E. coli using 13 C-D-glucose and 15 NH 4 Cl as the sole nutrient source. In recent years, the price of 13 C-D-glucose has almost tripled, making it essential to develop labelling methods that are as cost effective as possible. In this article, different parameters have been studied to achieve the most rational use of 13 C-D-glucose and an optimised method has been developed to obtain labeled proteins with high labelling, low 13 C-D-glucose consumption. Surprisingly, the optimised method is also simplier and does not require monitoring culture growth