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

The total protein mixture from the 50S subunit (TP-50) of the eubacterium T hermus thermophilus was characterized after blotting onto PVDF membranes fr om two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and sequenc ing. The proteins were numbered according to their primary structure simila rity with their counterparts from other species. One of them has been marke d with an asterisk, namely L*23, because unlike the other known ribosomal p roteins it shows a very low degree of homology. A highly acidic 5S rRNA binding protein, TL5, was characterized and compare d 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 ho mology 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, includin g TL5. Homologs to rpL25 and rpL26 were not found.