Ribosomal proteins of Tetrahymena thermophila. Correlation of one- and two-dimensional electrophoretic migration patterns and characterization of additional small and large subunit proteins

Molecular cloning and expression of a Tetrahymena pyriformis ubiquitin fusion gene coding for a 53-amino-acid extension protein

The genome of Tetrahymena pyriformis has been shown to contain a ubiquitin multigene family consisting of several polyubiquitin genes and at least one ubiquitin fusion gene. We report here the isolation and characterization of one genomic clone (pTU11), that encodes a ubiquitin extension protein. A comparison of the predicted amino acid sequence of the ubiquitin extension protein gene of T. pyriformis with those from other organisms indicated a high degree of homology. However, the Tetrahymena ubiquitin extension protein contains 53 and not 52 amino acids. This feature is different from all ubiquitin 52-amino-acid extension protein genes thus far sequenced. Furthermore, we found an array of four cysteine residues similar to those found in nucleic acid binding proteins. Also, the C-terminal sequence possesses a conserved motif which may represent a nuclear translocation signal. The ubiquitin 53-amino-acid extension protein gene encodes the smallest class of ubiquitin mRNAs in T. pyriformis.

Monovalent cation-dependent reversible phosphorylation of ribosomal protein S8 in growth arrested Tetrahymena: kinetics of formation, phosphoamino acids, and phosphopeptides of mono-, and diphosphorylated derivatives of protein S8

The kinetics of formation of mono-, and diphosphorylated derivatives of ribosomal protein S8 in Tetrahymena starving in the presence of Na+ have been determined, and the phosphoamino acids present in these derivatives have been identified. The mono-phosphorylated product, S8', contains only phosphoserine, and behaves kinetically as the precursor of the diphosphorylated product S8" which contains phosphoserine, and phosphothreonine. Tryptic digestion release a single major phosphoserine containing peptide from both S8' and S8", and a single phosphothreonine containing peptide from S8".

Protein-RNA crosslinking in the subunits of the cytoplasmic ribosome of Tetrahymena thermophila

Use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide to introduce RNA-protein crosslinks in the 40S and 60S subunits of the cytoplasmic ribosome of Tetrahymena thermophila is described, and proteins linked covalently to 17S and 26S ribosomal RNAs are identified. RNA-protein crosslinking is accompanied by extensive dimerization and aggregation of ribosomal subunits probably due to formation of interparticle protein-protein crosslinks.