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Crystal structure of the R463A mutant of human Glutamate dehydrogenaseCrystal structure of the R463A mutant of human Glutamate dehydrogenase
Structural highlights
Disease[DHE3_HUMAN] Defects in GLUD1 are the cause of familial hyperinsulinemic hypoglycemia type 6 (HHF6) [MIM:606762]; also known as hyperinsulinism-hyperammonemia syndrome (HHS). Familial hyperinsulinemic hypoglycemia [MIM:256450], also referred to as congenital hyperinsulinism, nesidioblastosis, or persistent hyperinsulinemic hypoglycemia of infancy (PPHI), is the most common cause of persistent hypoglycemia in infancy and is due to defective negative feedback regulation of insulin secretion by low glucose levels. In HHF6 elevated oxidation rate of glutamate to alpha-ketoglutarate stimulates insulin secretion in the pancreatic beta cells, while they impair detoxification of ammonium in the liver.[1] [2] [3] [4] Function[DHE3_HUMAN] May be involved in learning and memory reactions by increasing the turnover of the excitatory neurotransmitter glutamate (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGlutamate dehydrogenase (GDH) is found in all organisms and catalyzes the reversible oxidative deamination of L-glutamate to 2-oxoglutarate. Unlike GDH from bacteria, mammalian GDH exhibits negative cooperativity with respect to coenzyme, activation by ADP, and inhibition by GTP. Presented here are the structures of apo bovine GDH, bovine GDH complexed with ADP, and the R463A mutant form of human GDH (huGDH) that is insensitive to ADP activation. In the absence of active site ligands, the catalytic cleft is in the open conformation, and the hexamers form long polymers in the crystal cell with more interactions than found in the abortive complex crystals. This is consistent with the fact that ADP promotes aggregation in solution. ADP is shown to bind to the second, inhibitory, NADH site yet causes activation. The beta-phosphates of the bound ADP interact with R459 (R463 in huGDH) on the pivot helix. The structure of the ADP-resistant, R463A mutant of human GDH is identical to native GDH with the exception of the truncated side chain on the pivot helix. Together, these results strongly suggest that ADP activates by facilitating the opening of the catalytic cleft. From alignment of GDH from various sources, it is likely that the antenna evolved in the protista prior to the formation of purine regulatory sites. This suggests that there was some selective advantage of the antenna itself and that animals evolved new functions for GDH through the addition of allosteric regulation. Structural studies on ADP activation of mammalian glutamate dehydrogenase and the evolution of regulation.,Banerjee S, Schmidt T, Fang J, Stanley CA, Smith TJ Biochemistry. 2003 Apr 1;42(12):3446-56. PMID:12653548[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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