Proteins of the Thermus thermophilus ribosome. Purification of proteins from the large ribosomal subunit

Identification of the 50S ribosomal proteins from the Eubacterium Thermus thermophilus

The total protein mixture from the 50S subunit (TP-50) of the eubacterium Thermus thermophilus was characterized after blotting onto PVDF membranes from two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and sequencing. The proteins were numbered according to their primary structure similarity with their counterparts from other species. One of them has been marked with an asterisk, namely L*23, because unlike the other known ribosomal proteins it shows a very low degree of homology. A highly acidic 5S rRNA binding protein, TL5, was characterized and compared with the available primary structure information. Proteins L1 and L4 migrate similarly on 2D-PAGE. Protein L4, essential for protein biosynthesis, is N-terminally blocked and shows a strikingly low homology to other L4 proteins. In addition to L4, two other proteins, namely L10 and L11, were found to be N-terminally blocked. In conclusion, 33 proteins from the large subunit were identified, including TL5. Homologs to rpL25 and rpL26 were not found.

Sequencing and analysis of the Thermus thermophilus ribosomal protein gene cluster equivalent to the spectinomycin operon

To assess the organization of the Thermus thermophilus ribosomal protein genes, a fragment of DNA containing the complete S10 region and ten ribosomal protein genes of the spc region was cloned, using an oligonucleotide coding for the N-terminal amino acid (aa) sequence of T. thermophilus S8 protein as hybridization probe. The nucleotide sequence of a 4290 bp region between the rps17 and rpl15 genes was determined. Comparative analysis of this gene cluster showed that the gene arrangement (S17, L14, L24, L5, S14, S8, L6, L18, S5, L30 and L15) is identical to that of eubacteria. However, T. thermophilus ribosomal protein genes corresponding to the Escherichia coli S10 and spc operons are not resolved into two clusters: the stop codon of the rps17 gene (the last gene of the S10 operon in E. coli) and the start codon of the rpl14 gene (the first gene of the spc operon in E. coli) overlap. Most genes, except the rps14-rps8 intergenic spacer (69 bp), are separated by very short (only 3-7 bp) spacer regions or partially overlapped. The deduced aa sequences of T. thermophilus proteins share about 51-100% identities with the sequences of homologous proteins from thermophile Thermus aquaticus and Thermotoga maritima and 27-70% identities with the sequences of their mesophile counterparts.

Large-scale isolation of proteins of the large subunit from Escherichia coli ribosomes

A strategy has been developed and optimized that allows the isolation of proteins of the large subunit from Escherichia coli ribosomes and combines the following advantages: speed, applicability for the isolation of milligram amounts of a single protein, and preservation of the biological activity of the proteins. The method consists of the following steps: ion-exchange chromatography on MonoS and MonoQ, gel filtration on Sephadex 75, and salt washes. Eleven proteins can be purified by a single chromatographic step, and a combination of two steps enables the isolation of the other proteins.

A ribosomal protein from Thermus thermophilus is homologous to a general shock protein

The gene encoding the ribosomal protein from Thermus thermophilus, TL5, which binds to the 5S rRNA, has been cloned and sequenced. The codon usage shows a clear preference for G/C rich codons that is characteristic for many genes in thermophilic bacteria. The deduced amino acid sequence consists of 206 residues. The sequence of TL5 shows a strong similarity to a general shock protein from Bacillus subtilis, named CTC. The protein CTC is homologous in its N-terminal part to the 5S rRNA binding protein, L25, from E coli. An alignment of the TL5, CTC and L25 sequences displays a number of residues that are totally conserved. No clear sequence similarity was found between TL5 and other proteins which are known to bind to 5S rRNA. The evolutionary relationship of a heat shock protein in mesophiles and a ribosomal protein in thermophilic bacteria as well as a possible role of TL5 in the ribosome are discussed.