Inhibiting hexamer disassembly of human UDP-glucose dehydrogenase by photoactivated amino acid crosslinking
| Autor: | Jaleen Albers, Jiantao Guo, George Grady, Ashley M. Thelen, Melanie A. Simpson, Tong Ju, Joseph J. Barycki |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Models Molecular Uridine Diphosphate Glucose Light Stereochemistry Protein Conformation Trimer Dehydrogenase Random hexamer Uridine Diphosphate Glucose Dehydrogenase Biochemistry Cofactor Article Catalysis 03 medical and health sciences Protein structure Humans Amino Acids chemistry.chemical_classification 030102 biochemistry & molecular biology biology Substrate (chemistry) Photochemical Processes Amino acid Kinetics 030104 developmental biology Cross-Linking Reagents chemistry biology.protein NAD+ kinase Protein Multimerization Oxidation-Reduction |
| Popis: | The enzyme UDP-glucose dehydrogenase (UGDH) catalyzes the reaction of UDP-glucose to UDP-glucuronate through two successive NAD(+)-dependent oxidation steps. Human UGDH apoprotein is purified as a mixture of dimeric and hexameric species. Addition of substrate and cofactor stabilizes the oligomeric state to primarily the hexameric form. To determine if the dynamic conformations of hUGDH are required for catalytic activity, we used site-specific unnatural amino acid incorporation to facilitate cross-linking of monomeric subunits into predominantly obligate oligomeric species. Optimal cross-linking was achieved by encoding p-benzoyl-l-phenylalanine at position 458, normally a glutamine located within the dimer-dimer interface, and exposing the enzyme to long wavelength ultraviolet (UV) radiation in the presence of substrate and cofactor. Hexameric complexes were purified by gel filtration chromatography and found to contain significant fractions of dimer and trimer (approximately 50%) along with another 10% higher-molecular mass species. The activity of the cross-linked enzyme was reduced by almost 60% relative to that of the un-cross-linked UGDH mutant, and UV exposure had no effect on the activity of the wild-type enzyme. These results support a model for catalysis in which the ability to dissociate the dimer-dimer interface is as important for maximal enzyme function as has been previously shown for the formation of the hexamer. |
| Databáze: | OpenAIRE |
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