Conformational Changes During the Gating of a Potassium Channel Revealed by Structural Mass Spectrometry

SummaryPotassium channels are dynamic proteins that undergo large conformational changes to regulate the flow of K+ ions across the cell membrane. Understanding the gating mechanism of these channels therefore requires methods for probing channel structure in both their open and closed conformations. Radiolytic footprinting is used to study the gating mechanism of the inwardly-rectifying potassium channel KirBac3.1. The purified protein stabilized in either open or closed conformations was exposed to focused synchrotron X-ray beams on millisecond timescales to modify solvent accessible amino acid side chains. These modifications were identified and quantified using high-resolution mass spectrometry. The differences observed between the closed and open states were then used to reveal local conformational changes that occur during channel gating. The results provide support for a proposed gating mechanism of the Kir channel and demonstrate a method of probing the dynamic gating mechanism of other integral membrane proteins and ion channels.

Graphical AbstractFigure optionsDownload high-quality image (472 K)Download as PowerPoint slideHighlights
► Radiolytic labeling and mass spectroscopy is used to analyze KirBac3.1 gating
► Results identify conformationally sensitive residues near selectivity filter
► Largest structural changes is observed within the cavity of the membrane pore
► Results indicate direct evidence for dynamic role of G-loop and CD-loop for gating