Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An endonuclease, which is found only in the mitochondrion of the yeast Saccharomyces cerevisiae, has been purified. The protein has a sedimentation coefficient of 6.3 S, equivalent to a molecular weight of 105,000. The enzyme is active at pH 7.6, when it degrades single-stranded DNA about 10-times faster than double-stranded DNA, but at pH 5.4 only double-stranded DNA is degraded. In both cases the enzyme acts endonucleolytically, breaking a single phosphodiester bond at a random location within the DNA substrate. Mn2+ or Mg2+ are required for activity; Ca2+ and Zn2+ are ineffective cofactors. Enzyme activity at pH 7.6 is severely inhibited by low concentrations of NaCl or KCl, while activity at pH 5.4 is unaffected by salt. Ethidium bromide inhibits both the DNase activity at pH 5.4 and the activity with single-stranded DNA at pH 7.6, but has no effect on the DNase activity with double-stranded DNA at pH 7.6.
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PMID:Purification and properties of an endonuclease from the mitochondrion of Saccharomyces cerevisiae. 627 19

A single amino acid change transforms restriction enzyme NaeI to a topoisomerase and recombinase (NaeI-L43K) that shows no sequence similarity to these protein families. This transformation appears to result from coupled endonuclease and ligase domains. To further elucidate the relationship between NaeI-L43K and the topoisomerase protein family, we studied the effect of the topoisomerase inhibitors on NaeI-L43K activity. The intercalative drugs amsacrine, ellipticine, and daunorubicin inhibited NaeI-L43K, whereas the nonintercalating drugs camptothecin, VP-16, and oxolinic acid did not. Ethidium bromide also inhibited NaeI-L43K, implying that intercalation is responsible for its inhibition. The effects of the intercalative drugs on the DNA cleavage steps of NaeI and NaeI-L43K were compared. The drugs hardly inhibited DNA cleavage by wild type NaeI but completely inhibited DNA cleavage by NaeI-L43K. This difference in inhibition demonstrates that the L43K amino acid change sensitized NaeI to these drugs. Low concentrations of the intercalative drugs, except for ethidium bromide, enhance production of topoisomerase--DNA covalent intermediates but inhibited production of the NaeI-L43K--DNA covalent intermediate. These results imply some unique differences between DNA relaxation by NaeI-L43K and DNA topoisomerase. Concomitant with studying inhibition of the cleavage intermediate, NaeI-L43K was found to covalently bond with the 5' end of the cleaved DNA strand.
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PMID:Changing a leucine to a lysine residue makes NaeI endonuclease hypersensitive to DNA intercalative drugs. 875 63