Nucleotide and protein sequences of 60S ribosomal protein L17 from tobacco (Nicotiana tabacum L.).

More than 70 different proteins form two subunits of eukaryotic ribosomes and are major components of the total cellular protein. It has been reported that in various living organisms the biosynthesis of the different ribosomal proteins is regulated coordinately (Mager, 1988). Although some information concerning the primary structure of plant ribosoma1 proteins is available by isolating cDNA clones encoding the small subunit ribosomal proteins S11, S13, S14, S16, and S19 (Larkin et al., 1989; Gantt and Thompson, 1990; Lebrun and Freyssinet, 1991; Warskulat et al., 1991; Taylor et al., 1992; Joanin et al., 1993) and the large subunit ribosomal proteins L3 and L7 (Kim et al., 1990; Taylor et al., 1992), little is known about structure and regulation of most of the cytoplasmic ribosomal proteins in plants. Isolation of additional clones that code for other ribosomal proteins would facilitate the studies concerning whether plant ribosomal proteins are coordinately regulated during growth and development and whether their expression is controlled by any environmental factors. A cDNA library of mRNA from 3-d-old suspension-cultured tobacco (Nicotiana tabacum L.) cells was constructed in the XZapII vector (Stratagene, La Jolla, CA). The library was screened for highly expressing clones by the plaque hybridization method. A cDNA clone, TSC81, was present in the library at the frequency of about 1.4%. DNA sequencing revealed that the cDNA clone is 573 bp long and contains an open reading frame of 420 bp, which is flanked by a 18-bp leader and a 135-bp 3' untranslated region (Table I). The amino acid sequence deduced from the open reading frame showed 85% identity with the 60s ribosomal protein L17 from mammals (Chan et al., 1991), 76% identity with the yeast ribosomal protein L17, and approximately 30 to 50% identity with the 50s ribosomal protein L14 from various prokaryotic organisms. Most of the differences between the mammalian ribosomal protein L17 and tobacco protein are due to neutra1 substitutions. The length of the tobacco protein is identical with the mammalian ribosomal protein L17. The tobacco protein is composed of a high amount of basic amino acids, which is typical of ribosomal proteins. These results strongly suggest