The terminal protein of a linear mitochondrial plasmid is encoded in the N-terminus of the DNA polymerase gene in white-rot fungus Pleurotus ostreatus |
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Authors: | Eun-Kyoung Kim Jae-Hoon Jeong Hye Sook Youn Yong Bom Koo Jung-Hye Roe |
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Affiliation: | (1) School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea e-mail: jhroe@plaza.snu.ac.kr, KR;(2) Department of Microbiology, College of Natural Sciences, Inje University, Kimhae 621-749, Korea, KR |
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Abstract: | The gene structure and expression of the linear mitochondrial plasmids of the white-rot fungus Pleurotus ostreatus, pMLP1 and pMLP2, were analyzed. Cleavage by proteinase K and exonucleases indicated that the 5′ ends of pMLP1 and pMLP2
DNAs were associated with terminal proteins. Nucleotide sequencing of the entire pMLP1 DNA revealed that it consists of 9,879 bp
with terminal inverted repeat (TIR) sequences of 381 bp. The end sequence of TIR in pMLP1 is 3′-CCCCC-5′, similar to those
of Escherichia coli phage PRD1. The pMLP1 plasmid harbors two long open reading frames (ORF1 and ORF2) and at least one minor ORF (mORF1). The
deduced product of ORF1 is homologous to RNA polymerases of yeast mitochondria and several bacteriophages, whereas that of
ORF2 is homologous to the protein-primed DNA polymerases of family B type. The mORF1 encodes a highly basic protein, most
likely a TIR-binding protein, with no apparent sequence homology in the database. Expression of the predicted gene products
from pMLP1 in mitochondria was demonstrated by Western blot analysis using antibodies against various expressed regions of
pMLP1 ORFs. A plasmid-free strain, generated by curing with ethidium bromide, did not express any of these gene products.
Terminal proteins of 70 kDa (TP1) and 73 kDa (TP2) were identified from pMLP1 and pMLP2, respectively. Western blot analysis
indicated that TP1 was generated from the N-terminal half of the full-length product of ORF2 encoding a putative DNA polymerase.
Received: 9 February 2000 / Accepted: 18 July 2000 |
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Keywords: | Terminal protein DNA polymerase Linear mitochondrial plasmid Pleurotus ostreatus |
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