A low molecular weight DNA polymerase from wheat embryos.

Area of Science:

• Biochemistry
• Molecular Biology
• Plant Science

Background:

• The study of plant DNA polymerases is less advanced than that of animal or yeast counterparts.
• Understanding plant DNA polymerases is crucial for comprehending DNA replication and repair mechanisms in plants.

Purpose of the Study:

• To extensively purify and characterize a low molecular weight DNA polymerase from wheat embryos.
• To compare the biochemical and immunological properties of this plant DNA polymerase with known animal and other plant DNA polymerases.

Main Methods:

• Extensive purification of DNA polymerase CI from wheat embryos to apparent homogeneity.
• Biochemical characterization including molecular weight determination, inhibitor sensitivity, template preference, and amino acid analysis.
• Immunological characterization using polyclonal antibodies raised against DNA polymerase CI.

Main Results:

• A monomeric, basic protein (DNA polymerase CI) with a molecular weight of 52 kDa was purified.
• Antibodies against DNA polymerase CI showed limited cross-reactivity with other DNA polymerases, indicating specificity.
• DNA polymerase CI was insensitive to aphidicolin and phosphonoacetic acid but inhibited by ddTTP and N-ethylmaleimide.
• Spermine inhibited, while spermidine stimulated, enzyme activity.
• The enzyme showed a preference for poly dA-oligo dT template and recognized some synthetic polyribonucleotide templates.
• Amino acid analysis revealed striking similarity to animal DNA polymerase beta.

Conclusions:

• The purified wheat embryo DNA polymerase CI is a plant DNA polymerase highly similar to the low molecular weight animal DNA polymerase beta.
• This similarity suggests a conserved function, likely in nuclear DNA repair, across different eukaryotic kingdoms.