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Structural homology among calf thymus alpha-polymerase polypeptides
Nucleic Acids Research
|February 11, 1982
Summary
Highly purified calf thymus alpha-polymerase contains a large 118,000 Mr polypeptide with DNA polymerase activity. This polypeptide shares sequence homology with smaller polypeptides, suggesting a common precursor.
Area of Science:
- Molecular Biology
- Biochemistry
- Enzymology
Background:
- Calf thymus alpha-polymerase is a crucial enzyme involved in DNA replication.
- Previous studies suggested heterogeneity in the molecular weight of alpha-polymerase subunits.
Purpose of the Study:
- To characterize the polypeptide composition of purified calf thymus alpha-polymerase.
- To investigate the functional activity and structural relationships of different molecular weight polypeptides within the enzyme complex.
Main Methods:
- Purification of calf thymus alpha-polymerase.
- SDS-polyacrylamide gel electrophoresis with in situ DNA polymerase activity assay.
- Tryptic peptide mapping for primary structure analysis.
Main Results:
- A prominent 118,000 Mr polypeptide with DNA polymerase activity was identified.
- Five lower molecular weight polypeptides (54,000-64,000 Mr) were also detected.
- Tryptic peptide mapping revealed extensive primary structure homology between the 118,000 Mr polypeptide and some lower molecular weight polypeptides.
Conclusions:
- The findings provide the first evidence of sequence homology between high and low molecular weight polypeptides of calf thymus alpha-polymerase.
- These results support a model proposing a common precursor molecule (greater than 140,000 Mr) for the different subunits.