Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The RecBCD-K177Q enzyme has a lysine-to-glutamine mutation in the putative ATP-binding sequence of the RecD protein (Korangy, F., and Julin, D.A. (1992) J. Biol. Chem. 267, 1727-1732). We have compared the enzymatic properties of the RecBCD-K177Q enzyme with those of the wild-type RecBCD enzyme from Escherichia coli. The purified RecBCD-K177Q enzyme has ATP-dependent nuclease activity on double-stranded or denatured DNA which is reduced (4-14-fold less) compared with the wild type. The kcat and Km(ATP) for ATP hydrolysis stimulated by double-stranded DNA are both reduced in RecBCD-K177Q, so that kcat/Km(ATP) is relatively unaffected. The mutant enzyme is impaired in its ability to unwind DNA in an assay where single-stranded DNA is trapped by the single-stranded DNA binding protein and subsequently degraded by S1 nuclease. The mutant enzyme also produces fewer acid-soluble DNA nucleotides per ATP hydrolyzed than does the wild type, at low ATP concentrations (less than 20 microM).
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PMID:Enzymatic effects of a lysine-to-glutamine mutation in the ATP-binding consensus sequence in the RecD subunit of the RecBCD enzyme from Escherichia coli. 130 93

The influence of a C----G transversion at position 1 of the 30-base pair replication origin of bacteriophage phi X174 replicative form I DNA (phi X RFI) was examined in the RF----single-stranded circular DNA replication pathway catalyzed by the combined action of the purified phi X A protein, the Escherichia coli DNA polymerase III holoenzyme, rep helicase, and single-stranded DNA binding protein (Eisenberg, S., Scott, J.F., and Kornberg, A. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 1594-1597; Reinberg, D., Zipursky, S.L., and Hurwitz, J. (1981) J. Biol. Chem. 256, 13143-13151). RFI DNA containing this transversion was cleaved to RFII by the phi X A protein as effectively as DNA containing the wild-type origin. The altered duplex DNA, however, supported replication at a slower rate (3- to 4-fold) than the wild-type DNA due to a defect in the termination and reinitiation reactions catalyzed by the phi X A protein. This defect resulted in the accumulation of DNA products containing long single strands covalently joined to the mutant DNA. These single strands were susceptible to nuclease S1 and exonuclease VII attack. The defect in the template DNA containing C----G transversion was not corrected when this mutant origin was placed on the same strand with a wild-type origin. This double-origin DNA was also replicated poorly and led to the accumulation of large products, in contrast to the products formed with RFI DNA containing two wild-type 30-base pair replication origins on the same strand.
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PMID:Studies on the role of the phi X174 gene A protein in phi X viral strand synthesis. I. Replication of DNA containing an alteration in position 1 of the 30-nucleotide icosahedral bacteriophage origin. 297 11

We have found that preparations of DNA isolated from purulent sputum possess a novel activity which accelerates and stabilizes the binding of human leukocyte elastase to secretory leukoprotease inhibitor, a major endogenous antielastase in the respiratory tract. DNA in sputum is derived from the nuclear debris of disintegrated inflammatory leukocytes, and can attain concentrations ranging from 10(2) to 10(4) micrograms/ml, depending on the severity of pulmonary infection and inflammation. In the presence of 23 micrograms/ml DNA, a concentration lower than those found in most purulent sputa, the rate constant for association of secretory leukoprotease inhibitor with elastase is increased to 1.1 x 10(8) M-1s-1, 44-fold greater than that in the absence of DNA. The equilibrium dissociation constant for the enzyme-inhibitor complex drops to 0.7 pM, two orders of magnitude lower than that in the absence of DNA. The accelerating effect of DNA is further increased by thermal denaturation or by modification with exonuclease III, while it is significantly reduced by digestion with S1 nuclease or by binding of Escherichia coli single-stranded DNA binding protein. The results from these experiments indicate that the structural elements in sputum DNA that are responsible for the accelerating effect have the characteristics of single-stranded sites. Similar kinetic effects on elastase inhibition were also observed with human placental DNA and genomic DNAs from a variety of other species. These findings suggest that DNA in pulmonary secretions may participate in antielastase defense by promoting the binding of secretory leukoprotease inhibitor to leukocyte elastase. The results may have important implications for use of nuclease preparations in mucolytic therapy for cystic fibrosis.
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PMID:Accelerated binding of secretory leukoprotease inhibitor to human leukocyte elastase mediated by single-stranded sites in DNA from tracheobronchial mucus. 757 8