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Bacteriophage N4-coded 5'----3' exonuclease. Purification and characterization.
The Journal of Biological Chemistry
|August 15, 1986
Summary
Phage N4 DNA replication depends on a specific exonuclease enzyme. This study purified the phage-coded enzyme, revealing its dimeric structure and 5' to 3' DNA degradation activity essential for replication.
Area of Science:
- Molecular Biology
- Virology
- Enzymology
Background:
- Bacteriophage N4 DNA replication necessitates a specific phage-induced exonuclease.
- The genetic origin and enzymatic properties of this exonuclease were previously uncharacterized.
Purpose of the Study:
- To determine if the essential exonuclease activity in N4 replication is phage-coded.
- To purify and characterize the N4-encoded exonuclease enzyme.
Main Methods:
- Enzyme purification to homogeneity.
- Biochemical assays to determine substrate specificity and degradation direction.
- Analysis of enzyme quaternary structure in solution.
Main Results:
- The exonuclease activity responsible for N4 replication is indeed phage-coded.
- The purified enzyme is a dimer with a denatured molecular weight of 45,000.
- The enzyme exhibits 5' to 3' distributive degradation of duplex DNA, requiring an end for activity.
Conclusions:
- The characterized N4 exonuclease is a key enzyme in the phage's DNA replication machinery.
- Its specific mode of action suggests a role in processing DNA ends during replication.