Counter-intuitive method improves yields of isotopically-labeled proteins expressed in flask-cultured Escherichia coli

Abstract

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 13C, 15N and sometimes 2H. One of the most widely used methods to obtain these labeled proteins is heterologous expression of the proteins in E. coli using 13C-D-glucose and 15NH4Cl as the sole nutrient source. In recent years, the price of 13C-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 13C-D-glucose and an optimised method has been developed to obtain labeled proteins with high labelling, low 13C-D-glucose consumption. Surprisingly, the optimised method is also simplier and does not require monitoring culture growth