The Department of Biochemistry's weekly BCH 252 seminar series is presented this week by

Dr. Richard Debus, Professor, Department of Biochemistry, UC Riverside 

Seminar Title: "How Plants make Oxygen: New Insights into an Ancient Process"

Abstract: Oxygenic photosynthesis provides about half of our biosphere’s chemical energy and provides the food we eat and the O2 we breathe.  My laboratory’s goal is to elucidate the molecular mechanism of O2 formation in nature.  This process is catalyzed by the Mn4Ca cluster in Photosystem II (PSII).  The Mn4Ca cluster accumulates oxidizing equivalents in response to light-driven photochemical events within PSII and then oxidizes two molecules of H2O to O2 in the final step of a five-step cycle.  The Mn4Ca cluster catalyzes H2O oxidation far more efficiently than any synthetic catalyst because its protein environment choreographs the proton and electron transfer reactions associated with H2O oxidation and manages both substrate (H2O) access and proton egress.  My laboratory’s immediate goals are to (i) identify the dominant substrate access and proton egress pathways that link the Mn4Ca cluster with the thylakoid lumen, (ii) characterize the dynamic changes in the H-bond networks that comprise these pathways during the individual steps of the catalytic cycle, and (iii) obtain high resolution structures of intact PSII containing mutations of specific amino acid residues.  Our methods include FTIR difference spectroscopy, time-resolved IR spectroscopy, mass spectrometry, and cryo-EM. 

Seminar Host: Dr. Jikui Song; jikui.song@ucr.edu