Youngblom J, Schloss J A, Silflow C D
Mol Cell Biol. 1984 Dec;4(12):2686-96. doi: 10.1128/mcb.4.12.2686-2696.1984.
The two beta-tubulin genes of the unicellular green alga Chlamydomonas reinhardtii are expressed coordinately after deflagellation and produce two transcripts of 2.1 and 2.0 kilobases. Full-length cDNA clones corresponding to the transcript of each gene were isolated. DNA sequences were obtained from the cDNA clones and from cloned tubulin gene fragments. Both genes contained 1,332 base pairs of coding sequence, with only 19 nucleotide differences between the genes. Because all the differences occurred at the third base position of a codon and did not change the predicted amino acid sequence, we concluded that both beta-tubulin genes code for the same protein of 443 amino acids. The predicted amino acid sequence is 89 and 72% homologous with beta-tubulins from chicken and yeast cells, respectively. Each gene had three intervening sequences, which occurred at identical positions. Although the first two intervening sequences were not conserved between the two genes, the nucleotide sequence of the third intervening sequence was 89% conserved between the genes. The codon usage in the tubulin genes of C. reinhardtii was very biased: only 37 different codons were used. Striking differences occurred between the codons used in these nuclear genes and C. reinhardtii chloroplast genes.
单细胞绿藻莱茵衣藻的两个β-微管蛋白基因在鞭毛脱落后协同表达，并产生2.1和2.0千碱基的两种转录本。分离出了与每个基因转录本相对应的全长cDNA克隆。从cDNA克隆和克隆的微管蛋白基因片段中获得了DNA序列。两个基因都包含1332个碱基对的编码序列，基因之间只有19个核苷酸差异。由于所有差异都发生在密码子的第三个碱基位置，且未改变预测的氨基酸序列，我们得出结论，两个β-微管蛋白基因编码的是同一种由443个氨基酸组成的蛋白质。预测的氨基酸序列与鸡和酵母细胞的β-微管蛋白分别有89%和72%的同源性。每个基因有三个间隔序列，它们出现在相同的位置。虽然前两个间隔序列在两个基因之间不保守，但第三个间隔序列的核苷酸序列在基因之间有89%的保守性。莱茵衣藻微管蛋白基因的密码子使用非常有偏向性：只使用了37种不同的密码子。这些核基因和莱茵衣藻叶绿体基因所使用的密码子之间存在显著差异。
