In Situ Study of the Function of Bacterioruberin in the Dual-Chromophore Photoreceptor Archaerhodopsin-4

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 13C-13C spectra based on the complete chemical shift assignments, the 1.7-Å 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.

Oriented Nanoarchitectonics of Bacteriorhodopsin for Enhancing ATP Generation in a Fo F1 -ATPase-Based Assembly System

Energy conversion plays an important role in the metabolism of photosynthetic organisms. Improving energy transformation by promoting a proton gradient has been a great challenge for a long time. In the present study, we realize a directional proton migration through the construction of oriented bacteriorhodopsin (BR) microcapsules coated by F_o F₁ -ATPase molecular motors through layer-by-layer (LBL) assembly. The changes in the conformation of BR under illumination lead to proton transfer in a radial direction, which generates a higher proton gradient to drive the synthesis of adenosine triphosphate (ATP) by F_o F₁ -ATPase. Furthermore, to promote the photosynthetic activity, optically matched quantum dots were introduced into the artificial coassembly system of BR and F_o F₁ -ATPase. Such a design creates a new path for the use of light energy.

De novo resonance assignment of the transmembrane domain of LR11/SorLA in E. coli membranes

Membrane proteins perform many important cellular functions. Historically, structural studies of these proteins have been conducted in detergent preparations and synthetic lipid bilayers. More recently, magic-angle-spinning (MAS) solid-state NMR has been employed to analyze membrane proteins in native membrane environments, but resonance assignments with this technique remain challenging due to limited spectral resolution and high resonance degeneracy. To tackle this issue, we combine reverse labeling of amino acids, frequency-selective dipolar dephasing, and NMR difference spectroscopy. These methods have resulted in nearly complete resonance assignments of the transmembrane domain of human LR11 (SorLA) protein in E. coli membranes. To reduce background signals from E. coli lipids and proteins and improve spectral sensitivity, we effectively utilize amylose affinity chromatography to prepare membrane vesicles when MBP is included as a fusion partner in the expression construct.