Organization of genes encoding the L11, L1, L10, and L12 equivalent ribosomal proteins in eubacteria, archaebacteria, and eucaryotes.

Archaebacterial and eucaryotic cytoplasmic ribosomes contain proteins equivalent to the L11, L1, L10, and L12 proteins of the eubacterium Escherichia coli. In E. coli the genes encoding these ribosomal proteins are clustered, cotranscribed, and autogenously regulated at the level of mRNA translation. Genomic restriction fragments encoding the L11e, L1e, L10e, and L12e (equivalent) proteins from two divergent archaebacteria. Halobacterium cutirubrum and Sulfolobus solfataricus, and the L10e and L12e proteins from the eucaryote Saccharomyces cerevisiae have been cloned, sequenced, and analyzed. In the archaebacteria, as in eubacteria, the four genes are clustered and the L11e, L1e, L10e, and L12e order is maintained. The transcription pattern of the H. cutirubrum cluster is different from the E. coli pattern and the flanking genes on either side of the tetragenic clusters in E. coli, H. cutirubrum, and Sulfolobus solfataricus are all unrelated to each other. In the eucaryote Saccharomyces cerevisiae there is a single L10e gene and four separate L12e genes that are designated L12eIA, L12eIB, L12eIIA, and L12eIIB. These five genes are not closely linked and each is transcribed as a monocistronic mRNA; the L10e, L12eIA, L12eIB, and the L12eIIA genes are contiguous and uninterrupted, whereas the L12eIIB gene is interrupted by a 301 nucleotide long intron located between codons 38 and 39.