View source for 1uwz

[[Image:1uwz.gif|left|200px]]

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{{STRUCTURE_1uwz|  PDB=1uwz  |  SCENE=  }} 

'''BACILLUS SUBTILIS CYTIDINE DEAMINASE WITH AN ARG56- ALA 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==
1UWZ is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1UWZ 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:[http://www.ncbi.nlm.nih.gov/pubmed/15147186 15147186]
[[Category: Bacillus subtilis]]
[[Category: Cytidine deaminase]]
[[Category: Single protein]]
[[Category: Johansson, E.]]
[[Category: Larsen, S.]]
[[Category: Neuhard, J.]]
[[Category: Willemoes, M.]]
[[Category: Cdd]]
[[Category: Cytidine deaminase]]
[[Category: Hydrolase]]
[[Category: Pyrimidine metabolism]]
[[Category: Salvage]]
[[Category: Tetramer]]
[[Category: Zinc binding]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May  3 11:47:54 2008''