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Image of Dr. Chang Cui. She has black hair and is wearing a blue and white print blouse.

Biochemistry Seminar of Special Interest: Dr. Chang Cui (Harvard University), "Charge Transport and Conformational Gating in Metalloenzymes"

Event Type
Department of Biochemistry (HOST: Dr. Satish Nair)
Charles G. Miller Auditorium, B102 Chemical and Life Sciences Laboratory
Mar 3, 2023   12:00 pm  
Dr. Chang Cui
Cara Day
Originating Calendar
Biochemistry Department Seminars

 "Charge transport is essential to many biological processes including respiration, biodegradation and nucleic acid metabolism. Biological charge transfer can occur via electron transfer (ET) or proton-coupled electron transfer (PCET), which will be illustrated with several metal cofactors such as copper, heme, and non-heme iron. We will use  an  artificial  oxidase  to  demonstrate  intermolecular  ET  and  a  native  multi-copper  oxidase  to  illustrate intramolecular ET, both of which are related to oxygen reduction reaction. To exemplify biological PCET, we will discuss ribonucleotide reductase (RNR) in two aspects: proton transfer and conformational gating. RNRs play an essential role in the conversion of nucleotides to deoxynucleotides in all organisms. The E. coli class Ia RNR requires two homodimeric subunits, α and β. The active form is an asymmetric αα´ββ´ complex. The α subunit houses the site for nucleotide reduction initiated by a thiyl radical (C439•) and the β subunit, houses the diferric- tyrosyl radical (Y122•) that is essential for C439• formation. The reactions require a highly regulated and reversible long-range PCET pathway involving Y122•[β] ↔ W48?[β] ↔ Y356[β] ↔ Y731[α] ↔ Y730[α] ↔ C439[α]. Mutagenesis studies, transient absorption spectroscopy, and photochemical assays monitoring deoxynucleotide formation, collectively  indicate  that  the  E52[β],  R331[α],  E326[α]  and  E326[α´]  network  plays  the  essential  role  of  shuttling protons associated with Y356  oxidation from the interface to bulk solvent. This long-range PCET is kinetically regulated by conformational changes. The conformational gating can be resolved into two stages using 3,4- enylalanine (DOPA) as a probe: a global rearrangement and the side chain dynamics of Y731, a key residue during PCET."

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