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A covalent complex between retroviral integrase and nicked substrate DNA.
M Katzman1, J P Mack, A M Skalka
1Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033.
Summary
Retroviral integrase (IN) enzymes can process viral DNA and catalyze integration without external energy. Studies show IN forms a covalent bond with viral DNA, identifying key serine and threonine residues in the active site.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Retroviral integrase (IN) is essential for integrating viral DNA into host genomes.
- Understanding IN's mechanism is crucial for developing antiviral therapies.
Purpose of the Study:
- To investigate the catalytic mechanism of avian sarcoma-leukosis virus integrase (IN).
- To identify IN active-site residues involved in DNA processing and integration.
Main Methods:
- Purification of avian retroviral integrase (IN).
- In vitro assays using radiolabeled DNA substrates to assess IN activity.
- Computer-assisted sequence alignment of retroviral and retrotransposon IN proteins.
Main Results:
- Purified IN processed viral DNA termini and cleaved host DNA non-specifically.
- IN formed covalent phosphodiester bonds with the 5' ends of cleaved viral DNA.
- Serine and threonine residues were identified as key linkages, with one conserved serine and three conserved threonines across IN sequences.
Conclusions:
- A covalent IN-DNA intermediate is involved in retroviral integration.
- Conserved serine and threonine residues are candidate active-site residues crucial for IN function.