Document Detail

The junction-resolving enzyme T7 endonuclease I: quaternary structure and interaction with DNA.
MedLine Citation:
PMID:  9236119     Owner:  NLM     Status:  MEDLINE    
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.
M J Parkinson; D M Lilley
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of molecular biology     Volume:  270     ISSN:  0022-2836     ISO Abbreviation:  J. Mol. Biol.     Publication Date:  1997 Jul 
Date Detail:
Created Date:  1997-08-15     Completed Date:  1997-08-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985088R     Medline TA:  J Mol Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  169-78     Citation Subset:  IM    
Department of Biochemistry, The University of Dundee, UK.
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MeSH Terms
Bacteriophage T7 / enzymology*,  genetics
DNA, Viral / metabolism*
DNA-Binding Proteins / metabolism
Deoxyribonuclease I / chemistry*,  genetics,  metabolism
Protein Conformation*
Protein Denaturation
Urea / metabolism
Reg. No./Substance:
0/DNA, Viral; 0/DNA-Binding Proteins; 0/Solutions; 57-13-6/Urea; EC I

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