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Structure of the bifunctional dCTP deaminase-dUTPase from Methanocaldococcus jannaschii
Structural highlights
FunctionDCDB_METJA Bifunctional enzyme that catalyzes both the deamination of dCTP to dUTP and the hydrolysis of dUTP to dUMP without releasing the toxic dUTP intermediate. It also acts as a dUTP diphosphatase with a lower affinity for dUTP than for dCTP.[1] [2] 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 PubMedThe bifunctional dCTP deaminase-dUTPase (DCD-DUT) from Methanocaldococcus jannaschii catalyzes the deamination of the cytosine moiety in dCTP and the hydrolysis of the triphosphate moiety forming dUMP, thereby preventing uracil from being incorporated into DNA. The crystal structure of DCD-DUT has been determined to 1.88-A resolution and represents the first known structure of an enzyme catalyzing dCTP deamination. The functional form of DCD-DUT is a homotrimer wherein the subunits are composed of a central distorted beta-barrel surrounded by two beta-sheets and four helices. The trimeric DCD-DUT shows structural similarity to trimeric dUTPases at the tertiary and quaternary levels. There are also additional structural elements in DCD-DUT compared with dUTPase because of a longer primary structure. Four of the five conserved sequence motifs that create the active sites in dUTPase are found in structurally equivalent positions in DCD-DUT. The last 25 C-terminal residues of the 204-residue-long DCD-DUT are not visible in the electron density map, but, analogous to dUTPases, the C terminus is probably ordered, closing the active site upon catalysis. Unlike other enzymes catalyzing the deamination of cytosine compounds, DCD-DUT is not exploiting an enzyme-bound metal ion such as zinc or iron for nucleophile generation. The active site contains two water molecules that are engaged in hydrogen bonds to the invariant residues Ser118, Arg122, Thr130, and Glu145. These water molecules are potential nucleophile candidates in the deamination reaction. Structure of the bifunctional dCTP deaminase-dUTPase from Methanocaldococcus jannaschii and its relation to other homotrimeric dUTPases.,Johansson E, Bjornberg O, Nyman PO, Larsen S J Biol Chem. 2003 Jul 25;278(30):27916-22. Epub 2003 May 19. PMID:12756253[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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