Mapping membrane protein structure with fluorescence

Abstract

Membrane proteins regulate many cellular processes including signaling cascades, ion transport, membrane fusion, and cell-to-cell communications. Understanding the architecture and conformational fluctuations of these proteins is critical to understanding their regulation and functions. Fluorescence methods including intensity mapping, fluorescence resonance energy transfer (FRET), and photo-induced electron transfer, allow for targeted measurements of domains within membrane proteins. These methods can reveal how a protein is structured and how it transitions between different conformational states. Here, I will review recent work done using fluorescence to map the structures of membrane proteins, focusing on how each of these methods can be applied to understanding the dynamic nature of individual membrane proteins and protein complexes.

Figure 1

Fluorescent methods used to explore a membrane protein structure. In the center is the crystal structure of the acid sensing ion channel ASICS1 (PDB 2QTS) positioned with its transmembrane domains in a membrane [61]. Surrounding the structure are example fluorescent methods including FRET between the two fluorescent dyes Cy3 and Cy5, transition metal ion FRET between the dye bimane and a di-histidine bound metal, photo-induced electron transfer (PET) between bimane and a tryptophan, and a tetramethyl-rhodamine fluorophore undergoing an environment-induced fluorescent change. The approximate distance scales that each technique works over are indicated by the surrounding arrows.