Multifunctional proteins in Tetrahymena: 14-nm filament protein/citrate synthase and translation elongation factor-1 alpha

Int Rev Cytol. 1996;164:1-35. doi: 10.1016/s0074-7696(08)62383-9.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Citrate (si)-Synthase
  • Humans
  • Molecular Sequence Data
  • Peptide Elongation Factor 1
  • Peptide Elongation Factors / chemistry
  • Peptide Elongation Factors / genetics
  • Peptide Elongation Factors / physiology*
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics
  • Protozoan Proteins / physiology*
  • Tetrahymena / genetics
  • Tetrahymena / physiology*


  • Peptide Elongation Factor 1
  • Peptide Elongation Factors
  • Protozoan Proteins
  • 49K protein, Tetrahymena
  • Citrate (si)-Synthase