Spicer E K, Kavanaugh W M, Dallas W S, Falkow S, Konigsberg W H, Schafer D E
Proc Natl Acad Sci U S A. 1981 Jan;78(1):50-4. doi: 10.1073/pnas.78.1.50.
The genes coding for the heat-labile enterotoxin LT produced by Escherichia coli have been cloned into the plasmid pBR313. Using DNA derived from the resulting chimeric plasmid, we determined the nucleotide sequence of two regions of the gene coding for the enzymatically active A subunit of LT. Translation of the nucleotide sequence gives the primary structure of the NH2-terminal and COOH-terminal regions of the LT A subunit. This permits direct comparison of the LT A subunit with the A subunit of cholera toxin. Our results show that the two toxins possess homologous sequences, of varying degrees, in both regions of their primary structure. The order of the component A1 and A2 polypeptides is A1-A2. The nucleotide sequence predicts the existence of a signal sequence of 18 amino acids at the NH2-terminus of the A subunit.
编码大肠杆菌产生的热不稳定肠毒素LT的基因已被克隆到质粒pBR313中。利用从所得嵌合质粒衍生的DNA，我们确定了编码LT酶活性A亚基的基因两个区域的核苷酸序列。核苷酸序列的翻译给出了LT A亚基NH2末端和COOH末端区域的一级结构。这使得可以直接将LT A亚基与霍乱毒素的A亚基进行比较。我们的结果表明，这两种毒素在其一级结构的两个区域都具有不同程度的同源序列。组成A1和A2多肽的顺序是A1-A2。核苷酸序列预测在A亚基的NH2末端存在一个18个氨基酸的信号序列。
