Multifunctional proteins in Tetrahymena: 14-nm filament protein/citrate synthase and translation elongation factor-1 alpha.
One gene encoding a protein has been shown to have two entirely different functions. Such a phenomenon, which has been called "gene sharing," was first known in crystallins. We found two multifunctional proteins in the ciliated protozoan Tetrahymena: 14-nm filament protein and protein translation elongation factor 1-alpha (EF-1 alpha). The 14-nm filament protein has dual functions as a citrate synthase in mitochondria and as a cytoskeletal protein in cytoplasm. In cytoplasm, the 14-nm filament protein was involved in oral morphogenesis and in pronuclear behavior during conjugation. The observation that Tetrahymena intramitochondrial filamentous inclusions contain the 14-nm filament protein and that the citrate synthase activity of the 14-nm filament protein is decreased by polymerization and increased by depolymerization, suggests a possible modulating mechanism of citrate synthase activity by monomer-polymer conversion in mitochondria in situ. The EF-1 alpha functions as an F-actin-bundling protein and a 14-nm filament-associated protein as well as an elongation factor in protein synthesis. The F-actin-bundling activity of EF-1 alpha was regulated by Ca2+ and calmodulin. Here we review the properties and functions of two multifunctional proteins in Tetrahymena.
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Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
D000595:Amino Acid Sequence; D000818:Animals; D002950:Citrate (si)-Synthase; D006801:Humans; D008969:Molecular Sequence Data; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D013768:Tetrahymena / Q000235:genetics / Q000502:physiology*
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D015800:Protozoan Proteins; C067125:49K protein, Tetrahymena; D002950:Citrate (si)-Synthase