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Molecular and Cellular Biology, March 2000, p. 1816-1824, Vol. 20, No. 5
Institute of Molecular and Cellular Biology,
Tartu University,1 and Estonian
Biocentre,2 Tartu 51010, Estonia
Received 21 October 1999/Accepted 24 November 1999
A novel DNA helicase, a homolog of several prokaryotic helicases,
including Escherichia coli Rep and UvrD proteins, is
encoded by the Saccharomyces cerevisiae nuclear genome open
reading frame YOL095c on the chromosome XV. Our data demonstrate that
the helicase is localized in the yeast mitochondria and is loosely
associated with the mitochondrial inner membrane during biochemical
fractionation. The sequence of the C-terminal end of the 80-kDa
helicase protein is similar to a typical N-terminal mitochondrial
targeting signal; deletions and point mutations in this region abolish
transport of the protein into mitochondria. The C-terminal signal
sequence of the helicase targets a heterologous carrier protein into
mitochondria in vivo. The purified recombinant protein can unwind
duplex DNA molecules in an ATP-dependent manner. The helicase is
required for the maintenance of the functional
([rho+]) mitochondrial genome on both
fermentable and nonfermentable carbon sources. However, the
helicase is not essential for the maintenance of several defective
([rho
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
A DNA Helicase Required for Maintenance of the
Functional Mitochondrial Genome in Saccharomyces
cerevisiae
]) mitochondrial genomes. We also
demonstrate that the helicase is not required for transcription in mitochondria.
*
Corresponding author. Mailing address: Estonian
Biocentre, Riia 23, Tartu 51010, Estonia. Phone: 372-7-375037. Fax:
372-7-420286. E-mail: jsedman{at}ebc.ee.
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