Correlation of membrane protein conformational and functional dynamics

• Published in: Nature communications Vol. 12; no. 1; p. 4363
• Main Authors: Sanganna Gari, Raghavendar Reddy, Montalvo‐Acosta, Joel José, Heath, George R., Jiang, Yining, Gao, Xiaolong, Nimigean, Crina M., Chipot, Christophe, Scheuring, Simon
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.07.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 147/3; 631/1647/2204/1262; 631/57/2265; 631/57/2266; 631/57/2270/1140; 631/57/2282; 9/97; Atomic force microscopy; Biological Physics; Channel gating; Chemical Sciences; Correlation; Electrophysiology; Fluctuations; Humanities and Social Sciences; Ion channels; Ion flux; Membrane proteins; Membranes; Molecular dynamics; multidisciplinary; pH effects; Physics; Protein G; Proteins; Science; Science (multidisciplinary); Spectroscopy; Spectrum analysis; Temporal resolution
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24660-1

Conformational changes in ion channels lead to gating of an ion-conductive pore. Ion flux has been measured with high temporal resolution by single-channel electrophysiology for decades. However, correlation between functional and conformational dynamics remained difficult, lacking experimental techniques to monitor sub-millisecond conformational changes. Here, we use the outer membrane protein G (OmpG) as a model system where loop-6 opens and closes the β-barrel pore like a lid in a pH-dependent manner. Functionally, single-channel electrophysiology shows that while closed states are favored at acidic pH and open states are favored at physiological pH, both states coexist and rapidly interchange in all conditions. Using HS-AFM height spectroscopy (HS-AFM-HS), we monitor sub-millisecond loop-6 conformational dynamics, and compare them to the functional dynamics from single-channel recordings, while MD simulations provide atomistic details and energy landscapes of the pH-dependent loop-6 fluctuations. HS-AFM-HS offers new opportunities to analyze conformational dynamics at timescales of domain and loop fluctuations. High-speed atomic force microscopy height spectroscopy and single channel electrophysiology recordings are used to correlate conformational and functional dynamics of the model membrane protein, outer membrane protein G (OmpG). These techniques show that both states coexist and rapidly interchange in all conditions supported by molecular dynamics simulations.