Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

HeLa cells contain a high M.W. form of DNA ligase which can be completely converted to a low M.W. form. Stokes radius, frictional ratio, sedimentation coefficient, molecular weight, pH dependence, and heat inactivation rate of the two forms have been studied. The major properties of the two forms of DNA ligase in HeLa cells (in particular molecular weights and pH dependence) resemble those of the "dimer" and "monomer" structures described in cultured human cells (Pedrali, G., Spadari, S., Ciarrocchi, G., Pedrini, M., Falaschi, A. (1973) Eur. J. Biochem., 39 343) . In synchronized HeLa cells, the DNA ligase shows a two fold increase during S phase and parallels the increase in the DNA synthesis rate. DNA ligase increases in parallel with viral DNA synthesis after infection of HeLa cells with vaccinia and Herpes virus but its cofactor requirements and physical properties (including the dimer leads to monomer conversion) are unchanged, suggesting that the newly formed ligase is not virus-coded.
 ...
PMID:Properties of DNA ligase from uninfected and virus-infected HeLa cells. 0 21

Uracil-DNA glycosylase encoded in many species functions as a DNA repair enzyme that removes uracil residues from DNA. To investigate the potential function of uracil-DNA glycosylase encoded by human herpes-virus 6 (HHV-6), we sequenced a DNA clone (pSTY09), identified an open reading frame of 765 bp and compared the putative amino acid sequence with other uracil-DNA glycosylases, by computer analysis. The amino acid sequence of HHV-6 had similarities to other uracil-DNA glycosylases, with the highest degree of similarity to those of human cytomegalovirus and Epstein-Barr virus. Two strongly conserved regions in uracil-DNA glycosylase of other species also existed in HHV-6. The gene product which was expressed in Escherichia coli demonstrated uracil-DNA glycosylase activity. This is the first report to identify and characterize the uracil-DNA glycosylase gene in HHV-6.
 ...
PMID:Identification of human herpesvirus 6 uracil-DNA glycosylase gene. 807 33

We demonstrate that l-ATP is recognized by some enzymes that are involved in the synthesis of nucleotides and nucleic acids. l-ATP, as well as its natural d-enantiomer, acts as a phosphate donor in the reaction catalysed by human deoxycytidine kinase, whereas it is not recognized by either enantioselective human thymidine kinase or non-enantioselective herpes virus thymidine kinase. l-ATP strongly inhibits (Ki 80 microM) the synthesis of RNA primers catalysed by DNA primase associated with human DNA polymerase alpha, whereas RNA synthesis catalysed by Escherichia coli RNA polymerase is completely unaffected. Moreover, l-ATP competitively inhibits ATP-dependent T4 DNA ligase (Ki 25 microM), suggesting that it interacts with the ATP-binding site of the enzyme. Kinetic studies demonstrated that l-ATP cannot be used as a cofactor in the ligase-catalysed joining reaction. On the other hand, l-AMP is used by T4 DNA ligase to catalyse the reverse reaction, even though a high level of intermediate circular nicked DNA molecules accumulates. Our results suggest that a lack of enantioselectivity of enzymes is more common than was believed a few years ago, and, given the absence of selective constraints against l-nucleosides in Nature, this may depend on chance more than on evolutionary strategy.
 ...
PMID:L-ATP is recognized by some cellular and viral enzymes: does chance drive enzymic enantioselectivity? 989 5

The DNA repair enzyme uracil DNA glycosylase (UDG) catalyzes the hydrolysis of premutagenic uracil residues from single-stranded or duplex DNA, producing free uracil and abasic DNA. Here we report the high-resolution crystal structures of free UDG from Escherichia coli strain B (1.60 A), its complex with uracil (1.50 A), and a second active-site complex with glycerol (1.43 A). These represent the first high-resolution structures of a prokaryotic UDG to be reported. The overall structure of the E. coli enzyme is more similar to the human UDG than the herpes virus enzyme. Significant differences between the bacterial and viral structures are seen in the side-chain positions of the putative general-acid (His187) and base (Asp64), similar to differences previously observed between the viral and human enzymes. In general, the active-site loop that contains His187 appears preorganized in comparison with the viral and human enzymes, requiring smaller substrate-induced conformational changes to bring active-site groups into catalytic position. These structural differences may be related to the large differences in the mechanism of uracil recognition used by the E. coli and viral enzymes. The pH dependence of k(cat) for wild-type UDG and the D64N and H187Q mutant enzymes is consistent with general-base catalysis by Asp64, but provides no evidence for a general-acid catalyst. The catalytic mechanism of UDG is critically discussed with respect to these results.
 ...
PMID:Crystal structure of Escherichia coli uracil DNA glycosylase and its complexes with uracil and glycerol: structure and glycosylase mechanism revisited. 1009 Feb 82