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.