The role of Tyr34 in proton coupled electron transfer and product inhibition of manganese superoxide dismutase
Year: 2025
Type: article
Abstract: Human manganese superoxide dismutase (MnSOD) plays a crucial role in controlling levels of reactive oxygen species (ROS) by converting superoxide (O2●−) to molecular oxygen (O2) and hydrogen peroxide (H2O2) with proton-coupled electron transfers (PCETs). The reactivity of human MnSOD is determined by the state of a key catalytic residue, Tyr34, that becomes post-translationally inactivated by nitration in various diseases associated with mitochondrial dysfunction. We previously reported that Tyr34 has an unusual pKa due to its proximity to the Mn metal and undergoes cyclic deprotonation and protonation events to promote the electron transfers of MnSOD. To shed light on the role of Tyr34 MnSOD catalysis, we performed neutron diffraction, X-ray spectroscopy, and quantum chemistry calculations of Tyr34Phe MnSOD in various enzymatic states. The data identifies the contributions of Tyr34 in MnSOD activity that support mitochondrial function and presents a thorough characterization of how a single tyrosine modulates PCET catalysis.
Source: Nature Communications
Authors: Jahaun Azadmanesh, Katelyn Slobodnik, Lucas R. Struble, Jeffrey J. Lovelace, Erika A. Cone, Medhanjali Dasgupta, William E. Lutz, Siddhartha Kumar, Amarnath Natarajan, Leighton Coates, Kevin L. Weiss, Dean A. A. Myles, Thomas Kroll, Gloria E. O. Borgstahl
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $6,990
Funders: U.S. Department of Energy, U.S. Department of Health and Human Services, National Aeronautics and Space Administration, Nuclear Safety and Security Commission, National Institutes of Health, National Cancer Institute, National Institute of General Medical Sciences, Basic Energy Sciences, Biological and Environmental Research, Office of Experimental Program to Stimulate Competitive Research, Oak Ridge National Laboratory, SLAC National Accelerator Laboratory
Awards: G1286251239, G1663022414, Deciphering the Enzymatic Mechanism of Superoxide Dismutase, G2371548206, G262532246, G2812691261, G303061748, SUPEROXIDE DISMUTASES (SODS) ARE IMPORTANT ANTIOXIDANT ENZYMES THAT PROTECT ALL MVING CELLS AGAINST TOXIC OXYGEN METABOLITES, ALSO KNOWN AS REACTIVE, G315621713, G3418376741, G4235786860, G4581610328, G4642122183, G5570207115, SUPEROXIDE DISMUTASES (SODS) ARE IMPORTANT ANTIOXIDANT ENZYMES THAT PROTECT ALL LIVING CELLS AGAINST TOXIC OXYGEN METABOLITES ALSO KNOWN AS REACTIVE OXYGEN SPECIES (ROS). SODS ARE THE FIRST DEFENSE AGAINST PROPAGATION OF DAMAGING OXIDATIVE REACTIONS THROUGH ELIMINATION OF SUPEROXIDE. SUPEROXIDE IS GENERATED THROUGH NORMAL METABOLISM AND/OR IONIZING RADIATION. EACH CATALYTIC CYCLE DISMUTES TWO MOLECULES OF SUPEROXIDE TO OXYGEN AND HYDROGEN PEROXIDE VIA CYCLIC REDUCTION AND OXIDATION HALF REACTIONS USING THE ACTIVE SITE METAL ION. HUMANS HAVE CU/ZNSOD IN THE CYTOSOL AND EXTRACELLULAR SPACES AND MNSOD IN THEIR MITOCHONDRIA. MUTATIONS IN SOD LEAD TO AGING AND DEGENERATIVE DISEASES SUCH AS AMYOTROPHIC LATERAL SCLEROSIS DIABETES AND CANCER. THIS FLIGHT PROPOSAL WILL PROVIDE THE CRITICAL CRYSTAL SAMPLES NEEDED FOR A DETAILED STUDY OF HUMAN SOD. DESPITE THE BIOLOGICAL AND MEDICAL IMPORTANCE OF SOD THE COMPLETE ENZYMATIC MECHANISM IS STILL UNKNOWN. PRECISE STRUCTURAL DATA ARE NEEDED. THE BINDING SITES OF THE DIATOMIC SUBSTRATE AND PRODUCT AS WELL AS THE SOURCE OF THE PROTONS IN THE REACTION HAVE BEEN STUDIED BUT THEIR EXACT IDENTIFICATION HAS NOT BEEN POSSIBLE. THIS DETAILED INFORMATION CAN ONLY BE DETERMINED BY NEUTRON DIFFRACTION. COMPLEXES OF HUMAN MNSOD INCLUDING STRUCTURAL INTERMEDIATES AND MUTANTS WILL BE THE TARGETS FOR LARGE VOLUME CRYSTAL ( 1MM3) GROWTH FOR STRUCTURE DETERMINATION BY NEUTRON MACROMOLECULAR CRYSTALLOGRAPHY (NMC). THE QUIESCENT ENVIRONMENT AFFORDED BY MICROGRAVITY IS KNOWN TO GROW CRYSTALS LARGE ENOUGH FOR NEUTRON STUDIES NOT ONLY ARE THEY LARGE BUT THEIR QUALITY APPROACHES PERFECTION. IN 2001 THE BORGSTAHL LABORATORY SUCCESSFULLY GREW LARGE CRYSTALS OF SOD USING MICROGRAVITY CONDITIONS ON THE INTERNATIONAL SPACE STATION (ISS). WITH NASA S RENEWED INTEREST IN IMPLEMENTING THE MICROGRAVITY ENVIRONMENT ON THE ISS FOR PROTEIN CRYSTAL GROWTH WE WOULD LIKE TO MOVE FORWARD WITH THESE EXCITING EARLY MICROGRAVITY CRYSTALLIZATION RESULTS FOR SOD. EXISTING CRYSTALLIZATION HARDWARE THAT USES THE GRANADA CRYSTALLIZATION BOXES (GCB) FOR CAPILLARY COUNTERDIFFUSION PROTOCOLS WILL BE USED TO ACHIEVE THESE GOALS. A MICROGRAVITY ENVIRONMENT IS ESSENTIAL TO FORM A STABLE SUPERSATURATION GRADIENT TO OBTAIN THE LARGE HIGH QUALITY CRYSTALS REQUIRED FOR NMC. THEN NMC WILL BE PERFORMED WITH COLLABORATORS AT OAK RIDGE NATIONAL LABORATORY (ORNL). THE PRINCIPAL OUTCOME WILL BE TO IDENTIFY THE ROLE OF HYDROGEN ATOMS IN ENZYMATIC ACTIVITY DISCERN SUPEROXIDE FROM PEROXIDE AND WATER FROM HYDROXIDE ION BY THEIR PROTONATION STATE AND DECIPHER A STRUCTURE-BASED MECHANISM FOR HUMAN MNSOD MORE PRECISELY THAN FROM PREVIOUS X-RAY CRYSTALLOGRAPHIC MODELS DETERMINED FROM EARTH-GROWN CRYSTALS. THESE CONTRIBUTIONS WILL ALSO PROVIDE CRITERIA NEEDED FOR THE PROTEIN ENGINEERING OF DESIRABLE PROPERTIES INTO ENZYMATIC METAL CENTERS FOR PROTON COUPLED ELECTRON TRANSFER., G6438250069, G6550344761, G7283024673, G7396808078, Nebraska Research Network in Functional Genomics, G7863156295, G8925327636, G9000179768, A Synchrotron Radiation Structural Biology Resource, Buffett Cancer Center Support Grant, G911061179, G969889393
OpenAlex ID: W4407851884