Misra T K, Brown N L, Fritzinger D C, Pridmore R D, Barnes W M, Haberstroh L, Silver S
Proc Natl Acad Sci U S A. 1984 Oct;81(19):5975-9. doi: 10.1073/pnas.81.19.5975.
The mercuric ion-resistance operons of plasmid R100 (originally from Shigella) and transposon Tn501 (originally from a plasmid isolated in Pseudomonas) have been compared by DNA sequence analysis. The sequences for the first 1340 base pairs of Tn501 are given with the best alignment with the comparable 1319 base pairs of R100. The homology between the two sequences starts at base 58 after the end of the insertion sequence IS-1 of R100. The sequences include the transcriptional regulatory region, and the homology is particularly strong in regions just upstream from potential transcriptional initiation sites. The trans-acting regulatory gene merR consists of 180 base pairs in both cases and codes for a highly basic polypeptide of 60 amino acids, which is also rich in serine. The Tn501 and R100 merR genes differ in 25 of the 180 base positions, and the resulting polypeptides differ in seven amino acids. The regulatory region before the major transcription initiation site contains potential -35 and -10 sequences and dyad symmetrical sequences, which may be the merR binding sites for transcriptional regulation. The first structural gene, merT, encodes a highly hydrophobic polypeptide of 116 amino acids. The R100 and Tn501 merT genes differ in 17% of their positions, leading to 14 (12%) amino acid changes. This region had previously been shown to encode a protein governing membrane transport of mercuric ions. The second structural gene, merC, would give a 91 amino acid polypeptide with a hydrophobic amino-terminal segment. The Tn501 and R100 merC genes differ at 37 base positions, leading to 10 amino acid changes.
通过DNA序列分析，对质粒R100（最初来自志贺氏菌）和转座子Tn501（最初来自在假单胞菌中分离出的一种质粒）的汞离子抗性操纵子进行了比较。给出了Tn501前1340个碱基对的序列，并与R100的1319个可比碱基对进行了最佳比对。两个序列之间的同源性始于R100插入序列IS - 1末端后的第58个碱基。这些序列包括转录调控区，并且在潜在转录起始位点上游的区域中同源性特别强。反式作用调控基因merR在两种情况下均由180个碱基对组成，编码一种60个氨基酸的高度碱性多肽，该多肽也富含丝氨酸。Tn501和R100的merR基因在180个碱基位置中有25个不同，产生的多肽在7个氨基酸上不同。主要转录起始位点之前的调控区包含潜在的 - 35和 - 10序列以及二元对称序列，它们可能是merR用于转录调控的结合位点。第一个结构基因merT编码一种116个氨基酸的高度疏水多肽。R100和Tn501的merT基因在17%的位置上不同，导致14个（12%）氨基酸变化。该区域先前已被证明编码一种控制汞离子膜转运的蛋白质。第二个结构基因merC将产生一种具有疏水氨基末端片段的91个氨基酸的多肽。Tn501和R100的merC基因在37个碱基位置上不同，导致10个氨基酸变化。
