Chiariotti L, Alifano P, Carlomagno M S, Bruni C B
Mol Gen Genet. 1986 Jun;203(3):382-8. doi: 10.1007/BF00422061.
In this paper we report the nucleotide sequence of the hisD gene of Escherichia coli and of the his IE region of both E. coli and Salmonella typhimurium. The hisD gene codes for a bifunctional enzyme, L-histidinol:NAD+ oxidoreductase, of 434 amino acids with a molecular mass of 46,199 daltons. We established that the hisIE region of both S. typhimurium and E. coli is composed of a single gene and not, as previously believed, of two separate genes. The derived amino acid sequence indicates that the hisIE gene codes for a bifunctional protein of 203 amino acids with an approximate molecular mass of 22,700 daltons. We also determined the nucleotide sequence of a deletion mutant in S. typhimurium which abolishes the hisF and hisI functions but retains the hisE function. We deduced that the mutant produces a chimeric protein fusing the aminoterminal region of the upstream hisF gene to the carboxyl-terminal domain of the hisIE gene which encodes for the hisE function. In view of these results the structural and functional organization of the histidine operon in enteric bacteria needs to be revised. The operon is composed of only 8 genes and the pathway leading to the biosynthesis of the amino acid requires 11 enzymatic steps.
在本文中，我们报告了大肠杆菌hisD基因以及大肠杆菌和鼠伤寒沙门氏菌hisIE区域的核苷酸序列。hisD基因编码一种双功能酶，即L-组氨醇：NAD⁺氧化还原酶，由434个氨基酸组成，分子量为46,199道尔顿。我们确定，鼠伤寒沙门氏菌和大肠杆菌的hisIE区域均由单个基因组成，而不是如先前认为的由两个独立的基因组成。推导的氨基酸序列表明，hisIE基因编码一种由203个氨基酸组成的双功能蛋白，分子量约为22,700道尔顿。我们还确定了鼠伤寒沙门氏菌中一个缺失突变体的核苷酸序列，该突变体消除了hisF和hisI功能，但保留了hisE功能。我们推断，该突变体产生一种嵌合蛋白，将上游hisF基因的氨基末端区域与编码hisE功能的hisIE基因的羧基末端结构域融合。鉴于这些结果，肠道细菌中组氨酸操纵子的结构和功能组织需要修订。该操纵子仅由8个基因组成，而导致该氨基酸生物合成的途径需要11个酶促步骤。
