1ux0
From Proteopedia
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| - | | | + | {{STRUCTURE_1ux0| PDB=1ux0 | SCENE= }} |
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'''BACILLUS SUBTILIS CYTIDINE DEAMINASE WITH AN ARG56- GLN SUBSTITUTION''' | '''BACILLUS SUBTILIS CYTIDINE DEAMINASE WITH AN ARG56- GLN SUBSTITUTION''' | ||
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[[Category: Neuhard, J.]] | [[Category: Neuhard, J.]] | ||
[[Category: Willemoes, M.]] | [[Category: Willemoes, M.]] | ||
| - | [[Category: | + | [[Category: Cdd]] |
| - | [[Category: | + | [[Category: Cytidine deaminase]] |
| - | [[Category: | + | [[Category: Hydrolase]] |
| - | [[Category: | + | [[Category: Pyrimidine metabolism]] |
| - | [[Category: | + | [[Category: Salvage]] |
| - | [[Category: | + | [[Category: Tetramer]] |
| - | [[Category: | + | [[Category: Zinc binding]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 11:48:02 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 08:48, 3 May 2008
BACILLUS SUBTILIS CYTIDINE DEAMINASE WITH AN ARG56- GLN SUBSTITUTION
Overview
The zinc-containing cytidine deaminase (CDA, EC 3.5.4.5) is a pyrimidine salvage enzyme catalyzing the hydrolytic deamination of cytidine and 2'-deoxycytidine forming uridine and 2'-deoxyuridine, respectively. Homodimeric CDA (D-CDA) and homotetrameric CDA (T-CDA) both contain one zinc ion per subunit coordinated to the catalytic water molecule. The zinc ligands in D-CDA are one histidine and two cysteine residues, whereas in T-CDA zinc is coordinated to three cysteines. Two of the zinc coordinating cysteines in T-CDA form hydrogen bonds to the conserved residue Arg56, and this residue together with the dipole moments from two alpha-helices partially neutralizes the additional negative charge in the active site, leading to a catalytic activity similar to D-CDA. Arg56 has been substituted by a glutamine (R56Q), the corresponding residue in D-CDA, an alanine (R56A), and an aspartate (R56D). Moreover, one of the zinc-liganding cysteines has been substituted by histidine to mimic D-CDA, alone (C53H) and in combination with R56Q (C53H/R56Q). R56A, R56Q, and C53H/R56Q contain the same amount of zinc as the wild-type enzyme. The zinc-binding capacity of R56D is reduced. Only R56A, R56Q, and C53H/R56Q yielded measurable CDA activity, R56A and R56Q with similar K(m) but decreased V(max) values compared to wild-type enzyme. Because of dissociation into its inactive subunits, it was impossible to determine the kinetic parameters for C53H/R56Q. R56A and C53H/R56Q display increased apparent pK(a) values compared to the wild-type enzyme and R56Q. On the basis of the structures of R56A, R56Q, and C53H/R56Q an explanation is provided of kinetic results and the apparent instability of C53H/R56Q.
About this Structure
1UX0 is a Single protein structure of sequence from Bacillus subtilis. Full crystallographic information is available from OCA.
Reference
Structural, kinetic, and mutational studies of the zinc ion environment in tetrameric cytidine deaminase., Johansson E, Neuhard J, Willemoes M, Larsen S, Biochemistry. 2004 May 25;43(20):6020-9. PMID:15147186 Page seeded by OCA on Sat May 3 11:48:02 2008
