Scientists at Scripps Research have taken major steps to better understand the rules governing how membrane proteins act. In doing so, they have discovered novel activity patterns that may improve therapeutic approaches. The study, titled “Design principles of the common Gly-X6-Gly membrane protein building block,” was published on October 7, 2025, in the Proceedings of the National Academy of Sciences. The interdisciplinary research team, led by CERS assistant professor Marco Mravic, with significant contributions from master’s program alum Kiana Golden and her other co-collaborators.
This study was primarily concerned with understanding the Gly-X6-Gly motif. This repeating atomic motif is a hallmark of hundreds of membrane proteins. This motif is characterized by a small amino acid that occurs every seventh amino acid. It happens inside protein strands that pass through cell membranes. The researchers are particularly interested in how this recurring theme or motif influences the stability and behavior of proteins. Their hope is to design better therapeutic agents that can modulate these important proteins.
Unveiling the Gly-X6-Gly Motif
The Gly-X6-Gly motif is composed of an invariant sequence. Even pairs of identical small amino acids have differentiated positioning, as they take the same spot on every other turn of the helix. This remarkable structural property is paramount to the behavior of these often-vital membrane proteins. Having identified this motif as an obstacle in their earlier work, Mravic and his team set out to understand the basic rules that dictate this motif’s antics.
Marco Mravic, who contributed equally to the study, stresses the importance of understanding these proteins. He explained, “Billions and billions of dollars a year are being spent developing molecules to target membrane proteins. In order to modulate these proteins to fight disease, we need to understand how they work in the first place.” This announcement further highlights the need for increased understanding of membrane proteins to drive breakthroughs in drug discovery.
To facilitate their research, Kiana Golden developed a software program designed to identify amino acid sequences containing the Gly-X6-Gly motif. This powerful new tool enabled the team to design synthetic membrane proteins that were optimized for increased stability, providing their structures in a form suitable for detailed study.
Innovative Synthetic Proteins
The synthetic membrane proteins created by Golden and her teammates showed extraordinary stability, holding up to boiling point without breaking down. This durability is essential to be able to better understand mechanisms of action for these proteins in the context of whole living organisms. Mravic remarked on the challenges researchers typically face when investigating membrane proteins: “It’s usually really hard to study how membrane proteins behave within our bodies because as soon as we break them out of the cell, they want to fall apart.”
The reproducibility unlocked by their synthetic designs lays the groundwork for research and therapeutic advancement. These supercharged proteins let the team unlock new ways to study how membrane proteins behave, more powerful than any method used before.
Kiana Golden elaborated on their findings regarding the Gly-X6-Gly motif’s stability: “We found that the motif’s stability was driven by an unusual type of hydrogen bond that’s typically very weak, but when the motif is repeated, these weak hydrogen bonds all add up to make a very stable interaction.” This discovery has given us a more precise picture of how these structural motifs play a role in maintaining protein structure and activity.
Implications for Future Research
This research is about much more than academic curiosity. It anticipates significant progress in therapeutic approaches that focus on membrane proteins, which represent 30% of proteins and over 50% of drug targets. The findings from Mravic’s team suggest that their approach will vastly accelerate discoveries about membrane protein functionality and lead to improved therapies.
Mravic added that their method greatly accelerates the process of probing the inner workings of membrane proteins. Understanding this advance will make it possible to develop more effective therapies. The pharmaceutical industry is under tremendous pressure to find more efficient ways to design new drugs. These approaches need to allow engagement with large, multifaceted proteins.
The study included contributions from a diverse group of researchers at Scripps Research: Catalina Avarvarei, Charlie T. Anderson, Matthew Holcomb, Weiyi Tang, Xiaoping Dai, Minghao Zhang, Colleen A. Mailie, Brittany B. Sanchez, Jason S. Chen, and Stefano Forli. Their joint efforts highlight the cross-disciplinary aspects of this innovative work.