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PMID:9236119
| Citation |
Parkinson, MJ and Lilley, DM (1997) The junction-resolving enzyme T7 endonuclease I: quaternary structure and interaction with DNA. J. Mol. Biol. 270:169-78 |
|---|---|
| Abstract |
Endonuclease I is a DNA junction-selective resolving enzyme from bacteriophage T7. Using a nuclease-defective mutant that retains normal binding to DNA we show that the protein binds to four-way DNA junctions as a dimer, in common with other junction-resolving enzymes studied. Gel filtration and chemical crosslinking indicate that endonuclease I also exists in free solution as a dimer together with a tetramer and higher molecular mass aggregates. However, in marked contrast with other junction-resolving enzymes, there is no detectable subunit exchange under normal conditions. Only by exposure to 6 M urea could we induce subunit exchange, and this was used to generate heterodimeric species containing one active and one inactive subunit. Using a supercoil-stabilised cruciform substrate we demonstrate that an active subunit of endonuclease I can act as a junction-specific nuclease in a heterodimeric combination with an inactive subunit. However, the two subunits of a fully active homodimeric enzyme each cleave the phosphodiester backbone of a cruciform within the lifetime of the DNA-protein complex. |
| Links |
PubMed Online version:10.1006/jmbi.1997.1128 |
| Keywords |
Bacteriophage T7/enzymology; Bacteriophage T7/genetics; DNA, Viral/metabolism; DNA-Binding Proteins/metabolism; Deoxyribonuclease I/chemistry; Deoxyribonuclease I/genetics; Deoxyribonuclease I/metabolism; Dimerization; Protein Conformation; Protein Denaturation; Solutions; Urea/metabolism |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0008821: crossover junction endodeoxyribonuclease activity |
ECO:0000314: |
F |
After binding to the DNA junction as a dimer, the two subunits of the T7 endonuclease 1 catalyze cleavages independently but rather simultaneously before either is released from the junction (within the lifetime of the protein-junction complex) (Figure 6 and text around it, and Discussion). Similar characteristics have been found in T4 endonuclease VII. |
complete | ||||
Notes
See also
References
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