High-Speed AFM Images of Thermal Motion Provide Stiffness
Map of Interfacial Membrane Protein Moieties
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Abstract
The flexibilities of extracellular
loops determine ligand binding and activation of membrane receptors.
Arising from fluctuations in inter- and intraproteinaceous interactions,
flexibility manifests in thermal motion. Here we demonstrate that
quantitative flexibility values can be extracted from directly imaging
the thermal motion of membrane protein moieties using high-speed atomic
force microscopy (HS-AFM). Stiffness maps of the main periplasmic
loops of single reconstituted water channels (AqpZ, GlpF) revealed
the spatial and temporal organization of loop-stabilizing intraproteinaceous
H-bonds and salt bridges