Solid-state NMR structure determination of a membrane protein in E. coli cellular inner membrane

Structure determination of membrane proteins in native cellular membranes is critical to precisely reveal their structures in physiological conditions. However, it remains challenging for solid-state nuclear magnetic resonance (ssNMR) due to the low sensitivity and high complexity of ssNMR spectra of cellular membranes. Here, we present the structure determination of aquaporin Z (AqpZ) by ssNMR in Escherichia coli inner membranes. To enhance the signal sensitivity of AqpZ, we optimized protein overexpression and removed outer membrane components. To suppress the interference of background proteins, we used a dual-media expression approach and antibiotic treatment. Using 1017 distance restraints obtained from two-dimensional C-13-C-13 spectra based on the complete chemical shift assignments, the 1.7-angstrom ssNMR structure of AqpZ is determined in E. coli inner membranes. This cellular ssNMR structure determination paves the way for analyzing the atomic structural details for membrane proteins in native cellular membranes.

Automated summary

Determining the structure of membrane proteins in native cellular membranes using solid-state nuclear magnetic resonance (ssNMR) is challenging but essential for understanding their physiological structures. In this study, the structure of aquaporin Z (AqpZ) was successfully determined in Escherichia coli inner membranes through ssNMR. The researchers optimized protein overexpression and removed background proteins to enhance the signal sensitivity of AqpZ. This work paves the way for analyzing the atomic structural details of membrane proteins in native cellular membranes.