A DNA-POLYMERASE-BETA IN THE MITOCHONDRION OF THE TRYPANOSOMATID CRITHIDIA-FASCICULATA

被引:55
作者
TORRI, AF
ENGLUND, PT
机构
[1] Department of Biological Chemistry, Johns Hopkins Univ. Sch. of Medicine, Baltimore
关键词
D O I
10.1074/jbc.270.8.3495
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
We previously purified a Crithidia fasciculata mitochondrial DNA polymerase that has unusual properties. Unlike a conventional mitochondrial DNA polymerase gamma, this enzyme is small, non-processive, deficient in 3'-exonuclease activity, and error prone (Torri, A. F., Kunkel, T. A., and Englund, P. T. (1994) J. Biol. Chem. 269, 8165-8171), In all of these characteristics, the enzyme resembles DNA polymerase beta, a nuclear enzyme thought to be involved in DNA repair, We have now cloned and sequenced the gene for this enzyme. The mitochondrial polymerase has significant homology, about 33% identity at the amino acid level, with human DNA polymerase beta. However, sequence analysis of the clone revealed the presence of a cleaved N-terminal presequence, presumably a mitochondrial import signal, which resembles presequences on other C. fasciculata mitochondrial proteins, The polymerase's function may be to repair the many gaps in newly replicated kinetoplast (mitochondrial) DNA minicircles in this parasite, This enzyme is the first example of a mitochondrial DNA polymerase beta.
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页码:3495 / 3497
页数:3
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