Single-molecule visualization of dynamic transitions of pore-forming peptides among multiple transmembrane positions

Ying Li; Zhenyu Qian; Li Ma; Shuxin Hu; Daguan Nong; Chunhua Xu; Fangfu Ye; Ying Lu; Guanghong Wei; Ming Li

doi:10.1038/ncomms12906

Single-molecule visualization of dynamic transitions of pore-forming peptides among multiple transmembrane positions

Nat Commun. 2016 Sep 30:7:12906. doi: 10.1038/ncomms12906.

Authors

Ying Li¹, Zhenyu Qian², Li Ma¹, Shuxin Hu¹, Daguan Nong¹, Chunhua Xu¹, Fangfu Ye¹, Ying Lu¹, Guanghong Wei², Ming Li^{1

3}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
² State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai 200433, China.
³ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.

Abstract

Research on the dynamics of single-membrane proteins remains underdeveloped due to the lack of proper approaches that can probe in real time the protein's insertion depth in lipid bilayers. Here we report a single-molecule visualization method to track both vertical insertion and lateral diffusion of membrane proteins in supported lipid bilayers by exploiting the surface-induced fluorescence attenuation (SIFA) of fluorophores. The attenuation follows a d^-4 dependency, where d is the fluorophore-to-surface distance. The method is validated by observing the antimicrobial peptide LL-37 to transfer among five transmembrane positions: the surface, the upper leaflet, the centre, the lower leaflet and the bottom of the lipid bilayer. These results demonstrate the power of SIFA to study protein-membrane interactions and provide unprecedented in-depth understanding of molecular mechanisms of the insertion and translocation of membrane proteins.