Oral: How to "see" proton transfer during protein function using signature vibrational modes?

Proton transfer is a fundamental process in proteins, underlying bioenergetics, bio-catalysis, and bio-signaling. Understanding the functional mechanism of a protein often demands quantitative structural information on the proton-donor, the proton-acceptor, and the proton-transfer pathway. A main challenge in experimental study of proton transfer during a protein function is lack of effective tools to probe the protonation states of all structural members during proton transfer. The imidazole group of histidine can serve as a proton-donor, proton-acceptor, and a mediator during a proton transfer. We report how to use an integrated approach, combining Fourier transform infrared spectroscopy, histidine specific isotope-editing, site-specific mutation, and density-functional-theory based computational study to develop a general method for probing the three protonation states of histidine. Photoactive yellow protein, a light-activated blue light photoreceptor for bacterial phototaxis, was used as a model system in this study. We will discuss potential applications of this technology.