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'''Crystal structure of cytidine deaminase from Bacillus subtilis in complex with the inhibitor tetrahydrodeoxyuridine''' | '''Crystal structure of cytidine deaminase from Bacillus subtilis in complex with the inhibitor tetrahydrodeoxyuridine''' | ||
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[[Category: Mejlhede, N.]] | [[Category: Mejlhede, N.]] | ||
[[Category: Neuhard, J.]] | [[Category: Neuhard, J.]] | ||
[[Category: | [[Category: Cda]] | ||
[[Category: | [[Category: Cytidine deaminase]] | ||
[[Category: | [[Category: Pyrimidine salvage pathway]] | ||
[[Category: | [[Category: Zinc]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 21:54:08 2008'' | |||
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Revision as of 21:54, 2 May 2008
Crystal structure of cytidine deaminase from Bacillus subtilis in complex with the inhibitor tetrahydrodeoxyuridine
OverviewOverview
Cytidine deaminases (CDA, EC 3.5.4.5) are zinc-containing enzymes in the pyrimidine salvage pathway that catalyze the formation of uridine and deoxyuridine from cytidine and deoxycytidine, respectively. Two different classes have been identified in the CDA family, a homodimeric form (D-CDA) with two zinc ions per dimer and a homotetrameric form (T-CDA) with four zinc ions per tetramer. We have determined the first structure of a T-CDA from Bacillus subtilis. The active form of T-CDA is assembled of four identical subunits with one active site apiece. The subunit of D-CDA is composed of two domains each exhibiting the same fold as the T-CDA subunits, but only one of them contains zinc in the active site. The similarity results in a conserved structural core in the two CDA forms. An intriguing difference between the two CDA structures is the zinc coordinating residues found at the N-terminal of two alpha-helices: three cysteine residues in the tetrameric form and two cysteine residues and one histidine residue in the dimeric form. The role of the zinc ion is to activate a water molecule and thereby generate a hydroxide ion. How the zinc ion in T-CDA surrounded with three negatively charged residues can create a similar activity of T-CDA compared to D-CDA has been an enigma. However, the structure of T-CDA reveals that the negative charge caused by the three ligands is partly neutralized by (1) an arginine residue hydrogen-bonded to two of the cysteine residues and (2) the dipoles of two alpha-helices.
About this StructureAbout this Structure
1JTK is a Single protein structure of sequence from Bacillus subtilis. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the tetrameric cytidine deaminase from Bacillus subtilis at 2.0 A resolution., Johansson E, Mejlhede N, Neuhard J, Larsen S, Biochemistry. 2002 Feb 26;41(8):2563-70. PMID:11851403 Page seeded by OCA on Fri May 2 21:54:08 2008