1uio | pdb_00001uio
ADENOSINE DEAMINASE (HIS 238 ALA MUTANT)
Structural highlights
Function[ADA_MOUSE] Catalyzes the hydrolytic deamination of adenosine and 2-deoxyadenosine. Plays an important role in purine metabolism and in adenosine homeostasis. Modulates signaling by extracellular adenosine, and so contributes indirectly to cellular signaling events. Acts as a positive regulator of T-cell coactivation, by binding DPP4. Its interaction with DPP4 regulates lymphocyte-epithelial cell adhesion (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 PubMedHis 238, a conserved amino acid located in hydrogen-bonding distance from C-6 of the substrate in the active site of murine adenosine deaminase (mADA) and postulated to play an important role in catalysis, was altered into an alanine, a glutamate, and an arginine using site-directed mutagenesis. The Ala and Glu substitutions did not result in changes of the secondary or tertiary structure, while the Arg mutation caused local perturbations in tertiary structure and quenched the emission of one or more enzyme tryptophans. Neither the Glu or Arg mutations affected substrate binding affinity. By contrast, the Ala mutation enhanced substrate and inhibitor binding by 20-fold. The most inactive of the mutants, Glu 238, had a kcat/K(m) 4 x 10(-6) lower than the wild-type value, suggesting that a positive charge on His 238 is important for proper catalytic function. The Ala 238 mutant was the most active ADA, with a kcat/K(m) 2 x 10(-3) lower than the wild-type value. NMR spectroscopy and crystallography revealed that this mutant is able to catalyze hydration of purine riboside, a ground-state analog of the reaction. These results collectively show that His 238 is not required for formation of the hydroxylate used in the deamination and may instead have an important electrostatic role. Site-directed mutagenesis of histidine 238 in mouse adenosine deaminase: substitution of histidine 238 does not impede hydroxylate formation.,Sideraki V, Wilson DK, Kurz LC, Quiocho FA, Rudolph FB Biochemistry. 1996 Nov 26;35(47):15019-28. PMID:8942668[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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