Torturing Proteins–Useful Science or Just a Clever Experiment?

Philip Micheal Williams

Unfolding individual proteins by mechanical force has occupied biophysicists for the past 15 years or so. From the initial studies of the muscle protein titin, researchers have studied the effect of force on biomolecules ranging from small enzymes to large ribosomes. The majority of experiments use the atomic force microscope (AFM) as a means to stress proteins tethered between a surface and the probe, and elegant molecular biology approaches are used to produce constructs of repeating protein units which, when stretched and unfolded, produce a characteristic saw-toothed pattern that can be used to confirm complete or partial unfolding. In 2005 my colleague Jane Clarke and I noted that much of the work that had been done by then was to demonstrate the power of the AFM as a tool and that forced unfolding was beginning to move beyond a descriptive science towards a quantitative analysis of protein structure, stability and unfolding landscapes. We noted that the study of proteins that experience force in vivo was obvious but necessitating the use of new techniques such as optical tweezers (OT), and in discussing experiments to study the effects of solvent conditions, the direction of force, the marrying with computational simulations and the like, we were implying that the theoretical knowledge underpinning such quantification and necessary technological developments were in place. Some seven years later, it is interesting to see how the field has advanced and whether such quantitative analysis of our ‘obvious’ proteins has occurred.

DOI