Cα—H HYDROGEN BONDING DRIVES GxxxG ASSOCIATION IN A BIOLOGICAL MEMBRANE

The association of transmembrane helices (TMH) is critical in channels, receptors, transporters and enzymes. Misregulation of this association is linked to a variety of diseases such as cancer, viral infection, and neurodegeneration. However, the structural and energetic basis that underlies TMH oligomerization is only beginning to be understood. To better understand the forces of TMH association, I focused on understanding one of the most common ways for TMHs to associate: the GAS_right motif. The GAS_right motif is named for the Glycine, Alanine, and Serine amino acids, that make up the sequence motif (G/A/S)xxx(G/A/S) as well as a right handed crossing angle between two TMHs. GAS_right is the most common association motif for parallel TMH dimers and are optimized for the formation of Cα—H hydrogen bonds. Although these hydrogen bonds are theoretically important additions to stability, their specific contribution top association is still unclear. The difficulty of working with membrane proteins has hindered both structure determination as well as biophysical studies on the energetics of helix-helix association. To address this knowledge gap, we previously combined biophysical and computational techniques to investigate the forces that drive helix-helix interaction in the GAS_right motif. We created a prediction program, CATM, based on a minimal set of energy functions (van der Waals and hydrogen bonds) that can predict the structure of GAS_right motifs to near-atomic precision. Here, we present an approach that combines high-throughput structural prediction with experimental helix-helix association data. Together, these techniques produce a structure-based analysis of the forces that drive helix interactions in the context of the GAS_right motif.