Characterization of a putative fusogen encoded in a mitochondrial plasmid of Physarum polycephalum.
The mitochondrial plasmid mF induces mitochondrial fusion in zygotes and during sporulation in the true slime mold Physarum polycephalum. There are nine open reading frames (ORFs) in the mF plasmid, and it has been suggested that ORF640 encodes the mitochondrial fusogen. We prepared antisera directed against the ORF640 protein (ORF640p) in rabbits, and used it to localize this protein in mitochondria. Western blot analysis showed that ORF640p was produced only in the mitochondria of mF(+) strains, i.e., in cells that carried the mF plasmid. Proteinase K treatment of mitochondria isolated from the mF(+) strain suggested that the C-terminus coiled-coil (CC) region of ORF640p was exported from the matrix to the cytosol. Digitonin treatment confirmed this localization. West-Western blot analysis suggested that the CC region of ORF640p formed multimers and could interfere with an unknown mitochondrial protein in normal mitochondria. These results suggest that ORF640p is related to fusion of the outer mitochondrial membrane.
Takano
Hiroyoshi
H
Department of Biological Science, Faculty of Science, Kumamoto University, Kumamoto 860-8555, Japan, takano@kumamoto-u.ac.jp
Kawano
Shigeyuki
S
Sasaki
Narie
N
Kuroiwa
Haruko
H
Kuroiwa
Tsuneyoshi
T