Hairpin and dimer structures of linear plasmid-like DNAs in mitochondria of Paramecium caudatum.
The molecular structure of plasmid-like DNAs (designated type-II) which were isolated from mitochondria in the ciliated protozoan Paramecium caudatum was characterized. These type-II DNAs are always detected as a set of four kinds with sizes of 8.2, 4.1, 2.8 and 1.4 kb. The DNAs of 8.2 and 2.8 kb exist as dimers consisting of 4.1- and 1.4-kb monomer molecules, respectively. Electron microscopic observations indicated configurations of a hairpin structure that had a protruding end of single-stranded DNA in one terminus and a loop in the other terminus. The monomers stick together with base-pairing in opposite directions at the protruding end to form the dimers, suggesting the presence of inverted repeats. These unusual dimers may have a role in replication of the DNAs in which the monomers can serve as a primer for each other.
Endoh
H
H
Laboratory of Biology, Hosei University, Tokyo, Japan.
Yazaki
K
K
Takahashi
M
M
Tsukii
Y
Y
D000818:Animals; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000302:isolation & purification / Q000648:ultrastructure*; D016054:DNA, Protozoan / Q000737:chemistry / Q000302:isolation & purification / Q000648:ultrastructure*; D004587:Electrophoresis, Agar Gel; D008854:Microscopy, Electron; D008928:Mitochondria / Q000235:genetics*; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D010247:Paramecium / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping
D004272:DNA, Mitochondrial; D016054:DNA, Protozoan