Molecular cloning and nucleotide sequence of the gene for the ribosomal protein S11 from the archaebacterium Halobacterium marismortui

The gene encoding ribosomal protein S11 (Escherichia coli S15 homologue) from Halobacterium marismortui was cloned employing two synthetic oligonucleotide mixtures, 23 and 32 bases in length, as hybridization probes. The nucleotide sequence of the gene and the adjacent 5'- and 3'-flanking regions (1300 base pairs) were then determined by the dideoxy chain termination method. Comparison of the nucleotide sequence of the H. marismortui S11 gene with that of the E. coli S15 gene (rpsO) showed that the 3'-end of the S11 gene can be aligned with the entire E. coli S15 gene, sharing 44% identical nucleotides. It has been found that the S11 gene has a higher G + C content (G + C = 65%) than that of the E. coli S15 gene (G + C = 53%). This increase in G + C content specifically shows up as a preference for G + C in the 3rd position of the codon. Upstream of the S11 gene, an archaebacterial promoter sequence (GGACTTTCA) and a putative ribosomal binding site (GCGGT) have been found, 88 and 15 (or 24) base pairs from the initiation codon of the gene. In addition, an open reading frame could be identified immediately after the stop codon for the S11 gene. Northern blotting analysis using the S11 coding region as probe has shown that the S11 gene is located on a 2.4-kilobase mRNA, suggesting that it is cotranscribed with other downstream gene(s).