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. 1995 Apr;107(4):1277–1284. doi: 10.1104/pp.107.4.1277

Accuracy of Deoxynucleotide Incorporation by Soybean Chloroplast DNA Polymerases Is Independent of the Presence of a 3[prime] to 5[prime] Exonuclease.

J C Bailey 2nd 1, S Heinhorst 1, G C Cannon 1
PMCID: PMC157262  PMID: 12228434

Abstract

DNA polymerase was purified from soybean (Glycine max) chloroplasts that were actively replicating DNA. The main form (form I) of the enzyme was associated with a low level of 3[prime] to 5[prime] exonuclease activity throughout purification, although the ratio of exonuclease to polymerase activity decreased with each successive purification step. A second form (form II) of DNA polymerase, which elutes from DEAE-cellulose at a higher salt concentration than form I, was devoid of any exonuclease activity. To assess the potential function of the 3[prime] to 5[prime] exonuclease in proofreading, the fidelity of deoxynucleotide incorporation was measured for form I DNA polymerase throughout purification. Despite the steadily decreasing ratio of 3[prime] to 5[prime] exonuclease to polymerase activity, the extent of misincorporation by form I enzyme remained unchanged during the final purification steps, suggesting that the exonuclease did not contribute to the accuracy of DNA synthesis by this polymerase. Fidelity of form I DNA polymerase, when compared with that of form II, revealed a higher level of misincorporation for form I enzyme, a finding that is consistent with the exonuclease playing little or no role in exonucleolytic proofreading.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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