Accuracy of Deoxynucleotide Incorporation by Soybean Chloroplast DNA Polymerases Is Independent of the Presence of a 3[prime] to 5[prime] Exonuclease.
Plant Physiol
; 107(4): 1277-1284, 1995 Apr.
Article
em En
| MEDLINE
| ID: mdl-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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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Plant Physiol
Ano de publicação:
1995
Tipo de documento:
Article