Comparison of the structure of archaebacterial ribosomal proteins equivalent to proteins L11 and L1 from Escherichia coli ribosomes.

The sequences of two ribosomal proteins from two widely divergent species of archaebacteria, Halobacterium cutirubrum and Sulfolobus solfataricus, have been deduced from the structure of their respective genes. These two proteins were found to be equivalent to the L11 and L1 ribosomal proteins of the eubacterium Escherichia coli. Sequence comparison revealed that the archaebacterial L11e (equivalent to E. coli L11) proteins are longer than the eubacterial protein due to a C-terminal extension of about 30 residues. The archaebacterial L11e proteins, like the E. coli L11, are rich in proline residues; most of these are conserved. L11 is the most highly methylated protein in the E. coli ribosome. However, sites of methylation are generally not conserved in the archaebacterial L11e proteins. The region of highest sequence similarity between L11 and the archaebacterial L11e proteins is the N-terminal domain. This domain is believed to interact with release factor 1 during termination of translation. The amino acid sequences of the archaebacterial L1e proteins were compared to the eubacterial E. coli L1 and Bacillus stearothermophilus L1e sequences. The archaebacterial L1e proteins are slightly shorter at both their N- and C-termini. A region of high sequence similarity (7 of 14 residues) occurs near the center of the proteins.