Konigsberg W, Godson G N
Proc Natl Acad Sci U S A. 1983 Feb;80(3):687-91. doi: 10.1073/pnas.80.3.687.
Amino acid sequence and composition data of Escherichia coli dnaG primase protein and its tryptic peptides have confirmed that the dnaG gene contains an unusually high number of codons that are not frequently used in most E. coli genes. In 25 E. coli proteins analyzed the codons AUA, UCG, CCU, CCC, ACG, CAA, AAT, and AGG are infrequently used, occurring as 4% of the total codons in the reading frame and 11% and 10% in the nonreading frames. In dnaG they occur as 11% in the reading frame and 12% in the nonreading frames. The rpsU and rpoD genes, which flank the dnaG gene [Smiley, B. L., Lupski, J. R., Svec, P. S., McMacken, R. & Godson, G. N. (1982) Proc. Natl. Acad. Sci. USA 79, 4550-4554], however, have normal codon usage. Translational modulation using isoaccepting tRNA availability may therefore be part of the mechanism of keeping the dnaG gene expression low, while expression of the adjacent rpsU and rpoD genes on the same mRNA transcript is high.
大肠杆菌dnaG引发酶蛋白及其胰蛋白酶肽段的氨基酸序列和组成数据证实，dnaG基因含有大量在大多数大肠杆菌基因中不常用的密码子。在分析的25种大肠杆菌蛋白质中，密码子AUA、UCG、CCU、CCC、ACG、CAA、AAT和AGG不常用，在阅读框中占总密码子的4%，在非阅读框中分别占11%和10%。在dnaG中，它们在阅读框中占11%，在非阅读框中占12%。然而，位于dnaG基因两侧的rpsU和rpoD基因[Smiley, B. L., Lupski, J. R., Svec, P. S., McMacken, R. & Godson, G. N. (1982) Proc. Natl. Acad. Sci. USA 79, 4550 - 4554]具有正常的密码子使用情况。因此，利用同功tRNA可用性进行的翻译调控可能是使dnaG基因表达水平较低，而同一mRNA转录本上相邻的rpsU和rpoD基因表达水平较高的机制的一部分。
