A method for monitoring the folding and stability of proteins in single living cells is reported in a paper published online this week in Nature Methods. The method will allow more detailed understanding of protein function within cells.
The stability and dynamics of proteins are directly tied to their biological functions. However, most studies investigating protein dynamics are carried out on isolated proteins in dilute solutions, outside of the cell. In contrast, the interior of a cell is a very crowded environment where proteins can interact with many other biomolecules. To truly understand protein function, therefore, it must be studied within the confines of the cellular environment. Martin Gruebele and colleagues now report an approach to do so.
Proteins are very sensitive to temperature changes and will eventually unfold at high enough temperatures ― 'temperature jump' experiments are often used for studying the folding and stability of isolated proteins in solution. To adapt the approach to look at proteins in single living cells, the team fitted a fluorescence microscope with an infrared laser that can be used to induce very rapid temperature jumps. By labeling the protein of interest in the cell with fluorescent probes, it is possible to watch how its structure rapidly changes as the temperature is ramped higher and higher. This reveals information about the stability of the protein within the cell as well as the protein's unfolding kinetics.
Besides analyzing protein dynamics, the method could aid researchers studying other fast processes such as protein-protein interactions and heat-shock responses across populations of cells.