Tetrahymena intramitochondrial filamentous inclusions contain 14-nm filament protein/citrate synthase.
Tetrahymena 14-nm filament protein has been shown to have dual functions as a citrate synthase in mitochondria and as a cytoskeletal protein in oral morphogenesis and pronuclear behavior during conjugation. Immunofluorescence studies of the 14-nm filament protein/citrate synthase in mitochondria found that intense mitochondrial fluorescence remained unchanged in Tetrahymena cells taken from logarithmic growth phase to stationary phase. However, electron microscopic studies showed that electron-dense rod-shaped structures found in mitochondrial matrices tended to increase in Tetrahymena cells in the growth decline phase. The rods were composed of side-by-side straight filaments with diameters of approximately 14 to 16 nm. Serial sections revealed that in Tetrahymena cells in growth decline phase, one to four electron-dense rods existed in the matrices of every mitochondrion. Immunoelectron microscopy using an anti-14-nm filament antibody clearly showed that a filament bundle of the electron-dense rod was the bundle of polymerized filaments of 14-nm filament protein/citrate synthase. These results strongly suggest that dynamic monomer-polymer conversion of the 14-nm filament protein/citrate synthase in mitochondria depends upon the physiological conditions of Tetrahymena cells.
Numata
O
O
Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
Yasuda
T
T
Watanabe
Y
Y
D000818:Animals; D002455:Cell Division; D002950:Citrate (si)-Synthase / Q000032:analysis*; D003227:Conjugation, Genetic; D003598:Cytoskeletal Proteins / Q000032:analysis; D005455:Fluorescent Antibody Technique; D008840:Microfilament Proteins / Q000032:analysis*; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000201:enzymology / Q000648:ultrastructure*; D013769:Tetrahymena pyriformis / Q000502:physiology / Q000648:ultrastructure*
D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D002950:Citrate (si)-Synthase