Rosendahl G, Andreasen P H, Kristiansen K
Department of Molecular Biology, University of Odense, Denmark.
Gene. 1991 Feb 15;98(2):161-7. doi: 10.1016/0378-1119(91)90169-c.
The single-copy gene encoding ribosomal protein (r-protein) L21 in the macronucleus of the ciliate Tetrahymena thermophila was cloned and characterized. Sequencing of the L21 gene and a corresponding cDNA clone showed the gene to contain three introns, all located in the 3' half of the coding region. Primer extension and nuclease protection analyses revealed five transcription start points (tsp) 56-73 nucleotides upstream from the start codon. The uppermost tsp mapped to the first T in a sequence, TATAA, often found at tsp in T. thermophila. A comparison of amino acid sequences of r-proteins revealed that T. thermophila L21 belongs to a family of r-proteins that have been conserved in eubacteria, archaebacteria and eukaryotes. On the basis of structural and functional considerations, we suggest that the eukaryotic, like the prokaryotic, members of this protein family interact with the 5S RNA complex in ribosomes.
编码嗜热栖热四膜虫大核核糖体蛋白（r-蛋白）L21的单拷贝基因被克隆并进行了特性分析。L21基因及相应cDNA克隆的测序表明该基因含有三个内含子，均位于编码区的3'端。引物延伸和核酸酶保护分析揭示了五个转录起始点（tsp），位于起始密码子上游56-73个核苷酸处。最上游的tsp定位于序列TATAA中的第一个T，该序列在嗜热栖热四膜虫的tsp中经常出现。r-蛋白氨基酸序列的比较表明，嗜热栖热四膜虫L21属于在真细菌、古细菌和真核生物中保守的r-蛋白家族。基于结构和功能方面的考虑，我们认为该蛋白家族的真核成员，与原核成员一样，在核糖体中与5S RNA复合体相互作用。
