Novel Technique Allows for Protein Observation In Motion

A team of UC Santa Barbara scientists, led by Mark Sherwin, a physics professor, developed a technique to record proteins’ motion in a lifelike environment. Proteins play a crucial role in building blocks, receptors, processors, couriers, and catalysts, and this new approach can revolutionize our understanding of the methodology being protein function, as well as guide the design of proteins for specific purposes.

The paper published in Angewandte Chemie, a journal of the German Chemical Society, discusses the technique’s implementation. The researchers at UC Santa Barbara have tackled one of the grand challenges of modern science — observing proteins’ movement in action. The team made enormous progress in understanding the amino acid building blocks that make up a protein’s shape. However, even with the most powerful optical microscopes, proteins’ size is still a few nanometers, 100 times smaller than we can resolve.

Historically, the challenge for scientists has been observing proteins in action without affecting their structure. Many researchers study frozen proteins while utilizing a technique similar to stop-motion animation. They start the action, freeze the protein, capture an image, and repeat. This flash-freezing process can affect its structure, and the technique is difficult for both fast and slow movements. The team created a new strategy to look at proteins in a lifelike environment, eliminating the freezing aspect.

The technique developed by the researchers at UC Santa Barbara is known as TiGGER, or Time Resolved Gadolinium-Gadolinium Electron paramagnetic Resonance. The technique involves tagging two spots on the protein and tracking the distance between these labels as the protein unfolds and refolds. A charged gadolinium atom is the star of the technique. Its electrons line up, making it behave like a little magnet that aligns with or against the external field and begins to wobble. Scientists stabilize the gadolinium in a molecular cage to add some chemical scaffolding to link it with the protein.

The scientists strategically chose the spin label, which is big enough not to enter the protein’s core, where the functional cysteine is located. The precession of the gadolinium ion changes based on how close the two tags are to each other. The absorption of waves is measured, and if the amount of absorption changes with time, then the tags are moving. The authors selected a popular and versatile protein called AsLOV2, belonging to the light, oxygen, or voltage-sensitive family of proteins. The authors could derive the distance between the tags from the changes in the gadolinium’s precession.

These findings reveal how real-time proteomic tagging can be a new way to observe these macromolecules’ interactions with themselves and other parts of the cell. This technique can change our understanding of how proteins work and lead to designing proteins for specific purposes, such as drug development and toxicology.