A DNA polymerase from maize axes: its purification and possible role

Area of Science:

• Plant molecular biology
• Enzymology
• Biochemistry

Background:

• DNA polymerases are crucial for DNA replication and repair.
• Understanding plant DNA polymerases is essential for comprehending genome stability and development.

Purpose of the Study:

• To isolate and characterize DNA polymerase 2 from maize axes.
• To investigate the properties and potential function of this enzyme.

Main Methods:

• Protein extraction and purification using DEAE-cellulose, Heparin-Sepharose, Sephacryl S-300, and DNA cellulose chromatography.
• Enzyme activity assays, including pH and temperature optima.
• Inhibitor sensitivity analysis.
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting.

Main Results:

• DNA polymerase 2 was purified approximately 5000-fold.
• The enzyme requires Mg2+, is stimulated by K+, with optimal activity at pH 7.0 and 30-37°C.
• Inhibitor profiles were inconclusive for definitive polymerase type classification.
• Western blot analysis using an antibody against calf thymus DNA polymerase alpha suggested a high molecular mass (around 500 kDa) and cross-reactivity with several protein bands.
• Specific activity of polymerase 2 increased 100-fold during maize germination, unlike polymerase 3.

Conclusions:

• DNA polymerase 2 exhibits distinct biochemical properties and a significant increase in activity during maize germination.
• Evidence suggests polymerase 2 may be related to DNA polymerase alpha and potentially functions as a replicative enzyme in maize.
• Further studies are warranted to confirm its role in DNA replication.