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[Characteristics of nuclear endo-DNAase from rat liver by molecular mass and cationic dependence]
Abstract:
Study of the isoenzymatic spectrum of nuclear DNase from rat liver demonstrated that the extracts obtained in the presence of the protease inhibitor, PMSF, contained four polypeptides with molecular masses of 120, 54, 31 and 28 kDa possessing the endo-DNase activity. Long-term storage at -20 degrees C and autodigestion of the nuclei revealed the presence of additional polypeptides with a lower molecular mass and possessing an endo-DNase activity. Treatment of rat liver nuclear extracts with trypsin caused the appearance of an active polypeptide (M(r) 145 kDa). This finding and the multiplicity of endo-DNases of different molecular masses suggest the existence of a precursor possessing a much higher molecular mass. Chromatographic separation of endo-DNases on Sephacryl S-300 revealed three fractions of 400 and more kDa possessing a Ca2+/Mg(2+)-dependent activity, however, only after trypsin treatment.
Insights
Rat liver nuclear extracts contain multiple endo-DNase enzymes. These enzymes, with varying molecular masses, suggest a high molecular mass precursor, potentially activated by trypsin.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Context:
- Nuclear DNases (deoxyribonucleases) play crucial roles in DNA metabolism and cellular processes.
- Understanding the isoenzymatic spectrum of nuclear DNases is essential for elucidating their functions.
- Rat liver is a common model system for studying fundamental biological processes.
Purpose:
- To investigate the isoenzymatic spectrum of nuclear DNase from rat liver.
- To identify the molecular masses and characteristics of active DNase polypeptides.
- To explore the potential existence of a high molecular mass precursor for nuclear DNases.
Summary:
- Nuclear extracts from rat liver, when protected with PMSF, revealed four endo-DNase polypeptides (120, 54, 31, and 28 kDa).
- Extended storage and autodigestion led to lower molecular mass active polypeptides.
- Trypsin treatment generated a 145 kDa active polypeptide, suggesting a larger precursor.
- Chromatography indicated high molecular mass fractions (>400 kDa) with Ca2+/Mg2+-dependent activity, requiring trypsin activation.
Impact:
- The findings suggest a precursor model for rat liver nuclear endo-DNases.
- This research contributes to the understanding of DNA processing and regulation.
- Identifies potential targets for further biochemical and functional studies.