GXXXG‐Mediated Parallel and Antiparallel Dimerization of Transmembrane Helices and Its Inhibition by Cholesterol: Single‐Pair FRET and 2D IR Studies

Small‐residue‐mediated interhelical packings are ubiquitously found in helical membrane proteins, although their interaction dynamics and lipid dependence remain mostly uncharacterized. We used a single‐pair FRET technique to examine the effect of a GXXXG motif on the association of de novo designed (AALALAA)3 helices in liposomes. Dimerization occurred with sub‐second lifetimes, which was abolished by cholesterol. Utilizing the nearly instantaneous time‐resolution of 2D IR spectroscopy, parallel and antiparallel helix associations were identified by vibrational couplings across helices at their interface. Taken together, the data illustrate that the GXXXG motif controls helix packing but still allows for a dynamic and lipid‐regulated oligomeric state. Das Motiv ist wichtig: Transmembranäre Helixmodelle mit GXXXG‐Motiv wurden hergestellt, um die Effekte dieses Motivs sowie der Lipidzusammensetzung auf die Helixassoziation zu untersuchen. Einzelpaar‐FRET‐ und 2D‐IR‐Experimente offenbarten die dynamische Natur, spezifische Grenzflächen und eine hohe Cholesterol‐Sensitivität der GXXXG‐vermittelten Wechselwirkungen, wodurch die Funktion des Membranproteins aktiv reguliert werden kann.