Single-molecule fluorescence vistas of how lipids regulate membrane proteins

Abstract

The study of membrane proteins is undergoing a golden era, and we are gaining unprecedented knowledge on how this key group of proteins works. However, we still have only a basic understanding of how the chemical composition and the physical properties of lipid bilayers control the activity of membrane proteins. Single-molecule (SM) fluorescence methods can resolve sample heterogeneity, allowing to discriminate between the different molecular populations that biological systems often adopt. This short review highlights relevant examples of how SM fluorescence methodologies can illuminate the different ways in which lipids regulate the activity of membrane proteins. These studies are not limited to lipid molecules acting as ligands, but also consider how the physical properties of the bilayer can be determining factors on how membrane proteins function.

Principles of Resonance Energy Transfer

“…Conformational changes in the 10 µs to 10 s range can be best studied using diffusion‐based smFRET (Tomov et al., 2012). With the established and improved smFRET schemes, several problems have been studied, such as the structural dynamics of ion channels (Martinac, 2017), membrane proteins (Castell, Dijkman, Wiseman, & Goddard, 2018; Ward, Ye, Schuster, Wei, & Barrera, 2021; Yang, Xu, Wang, Chen, & Zhao, 2021), intrinsically disordered proteins (LeBlanc, Kulkarni, & Weninger, 2018; Metskas & Rhoades, 2020), DNA polymerases (Millar, 2022), and DNA nanostructures (Pal, 2022). The multicolor version of smFRET, in which more than one donor‐acceptor pair is used, can provide even more information about protein‐DNA interactions, chromatin remodeling and even protein translation (Feng et al., 2021).…”

Cholesterol inhibits assembly and activation of the EphA2 receptor

“…Membrane lipids often affect integral membrane protein conformation and activity, and these lipid effects can occur through direct (allosteric) binding or by indirect mechanisms 13,14 . The composition of the membrane also impacts the activity and spatial recruitment of intracellular interacting partners.…”

Reconstitution of purified membrane protein dimers in lipid nanodiscs with defined stoichiometry and orientation using a split GFP tether

“…, ( 1 , 2 )). In addition, many membrane proteins are known to form homodimers or heterodimers or larger oligomers ( 3 ), which are sometimes mediated by specific lipids ( 4 , 5 , 6 , 7 ). In some cases, such as class A G-protein–coupled receptors (GPCRs), oligomerization is transient or weak ( 8 ), and intramembrane interactions are disrupted during detergent extraction.…”