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J. Biol. Chem., Vol. 278, Issue 49, 49095-49101, December 5, 2003

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Trypanosoma brucei Has Two Distinct Mitochondrial DNA Polymerase Enzymes^*

Tina T. Saxowsky, Gunjan Choudhary, Michele M. Klingbeil, and Paul T. Englund¶

From the Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205

In higher eukaryotes, DNA polymerase (pol) resides in the nucleus and participates primarily in DNA repair. The DNA polymerase from the trypanosomatid Crithidia fasciculata, however, was the first mitochondrial enzyme of this type described. Upon searching the nearly completed genome data base of the related parasite Trypanosoma brucei, we discovered genes for two pol -like proteins. One is 70% identical to the C. fasciculata pol and is likely the homolog of this enzyme. The other, although 30% identical within the polymerase region, has unusual structural features including a short C-terminal tail and a long N-terminal extension rich in prolines, alanines, and lysines. Both proteins, when expressed recombinantly, are active as DNA polymerases and deoxyribose phosphate lyases, but their polymerase activity optima differ with respect to pH and KCl and MgCl₂ concentrations. Remarkably, green fluorescent protein fusion proteins and immunofluorescence demonstrate that both are mitochondrial, but their locations with respect to the mitochondrial DNA (kinetoplast DNA network) in this organism are strikingly different.

Received for publication, August 4, 2003 , and in revised form, August 28, 2003.

^* This work was funded by National Institutes of Health Grant GM27608. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Supported by a Fannie and John Hertz Graduate Fellowship. Present address: Dept. of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd. NE, Atlanta, GA 30322.

Present address: Dept. of Microbiology, University of Massachusetts, 639 N. Pleasant St., Amherst, MA 01003.

^¶ To whom correspondence should be addressed: Dept. of Biological Chemistry, Johns Hopkins School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205. Tel.: 410-955-3790; Fax: 410-955-7810; E-mail: penglund{at}jhmi.edu.

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