Endonuclease activity of venom phosphodiesterase specific for single-stranded and superhelical DNA
A homogeneous preparation of venom phosphodiesteraseus adamanteus possesses an intrinsic endonuclease activity, specific for superhelical (form I) and single-stranded DNA. The phosphodiesterase degrades single-stranded T/sub 7/ DNA by endonucleolytic cleavages. Duplex T/sub 7/ DNA is hydrolyzed by the liberation of acid-soluble products simultaneously from the 3' and 5' termini but without demonstrable internal scissions in duplex regions. Since venom phosphodiesterase is known to hydrolyze oligonucleotides stepwise from the 3' termini, the cleavage at the 5' end of duplex T/sub 7/ DNA is ascribed to an endonuclease activity. Form I PM2 DNA is nicked to yield first relaxed circles and then linear DNA which is subsequently hydrolyzed only from the chain termini. The linear duplex DNA intermediates consist of a discrete series of fragments (11 are usually resolved on agarose gels) with initial molecular weights ranging from 6.3 x 10/sup 6/ (the intact PM2 DNA size) to approximately 1 x 10/sup 6/. The cleavage of the form I molecule must, therefore, occur at a limited number of unique sites. The enzyme also cleaves nonsuperhelical, covalently closed circular PM2 DNA but at a 10/sup 4/ times slower rate. Both the endonuclease activity on form I DNA and the known exonuclease activity co-migrate on polyacrylamide gels, are optimally active at pH 9, are stimulated by small concentrations of Mg/sup 2 +/, and are similarly inactivated by heat, reducing agents, and EDTA.
- Research Organization:
- Roswell Park Memorial Inst., Buffalo
- OSTI ID:
- 6800419
- Journal Information:
- J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 252:23; ISSN JBCHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BIOLOGICAL EFFECTS
CHEMICAL REACTIONS
DECOMPOSITION
DNA
ENZYMATIC HYDROLYSIS
ENZYMES
ESTERASES
ESTERS
HYDROLASES
HYDROLYSIS
LYSIS
NUCLEASES
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORIC ACID ESTERS
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