Nakamura K, Inouye M
Proc Natl Acad Sci U S A. 1980 Mar;77(3):1369-73. doi: 10.1073/pnas.77.3.1369.
The Serratia marcescens gene for the outer membrane lipoprotein (lpp) was cloned in lambda phage vector Charon 14. The recombinant phage was very unstable, and the lpp gene with a 300-base-pair deletion at the transcription termination site was further cloned in pBR322. The DNA sequence of 834 base pairs encompassing the lpp gene was determined and compared with that of the Escherichia coli lpp gene. The sequence comparisons exhibit several unique features. (i) The promoter region is highly conserved (84% homology) and has an extremely high A+T content (78%) as in E. coli (80%). (ii) The 5' nontranslated region of the lipoprotein mRNA is also highly conserved (95% homology). (iii) In the DNA sequence corresponding to the signal peptide of this secretory protein, there are three drastic changes, including addition of one base pair and deletion of four base pairs in S. marcescens as compared to E. coli. The resultant alterations in the amino acid sequence, however, do not change the basic properties of the signal peptide, which are assumed to be essential for its function in the secretory mechanism. (iv) The DNA sequence from the amino terminus to the 51st residue of the mature lipoprotein is highly conserved (95% homology) and there is no amino acid substitution. (v) The DNA sequence corresponding to the seven amino acid residues at the carboxyl terminus has only 42% homology, resulting in four amino acid substitutions. (vi) Within the section of 40 base pairs beginning with the termination codon (UAA) and ending immediately before the oligo(T) transcription termination site in the E. coli lpp gene, there is about 60% homology. However, after this section, there is no obvious homology between the two sequences, probably because of a deletion of 300 base pairs at this region. (vii) Seven stable stem-and-loop structures could be formed in the mRNA region. (viii) Alterations in the third position of codons used in the lpp gene suggest that the gene has evolved somewhat differently from other genes in S. marcescens.
粘质沙雷氏菌外膜脂蛋白（lpp）基因被克隆到λ噬菌体载体Charon 14中。重组噬菌体非常不稳定，转录终止位点处有300个碱基对缺失的lpp基因进一步被克隆到pBR322中。测定了包含lpp基因的834个碱基对的DNA序列，并与大肠杆菌lpp基因的序列进行了比较。序列比较显示出几个独特的特征。（i）启动子区域高度保守（84%同源性），并且与大肠杆菌（80%）一样具有极高的A+T含量（78%）。（ii）脂蛋白mRNA的5'非翻译区也高度保守（95%同源性）。（iii）在对应于这种分泌蛋白信号肽的DNA序列中，有三个显著变化，与大肠杆菌相比，粘质沙雷氏菌中有一个碱基对的添加和四个碱基对的缺失。然而，氨基酸序列的这些变化并没有改变信号肽的基本特性，而这些特性被认为对其在分泌机制中的功能至关重要。（iv）从成熟脂蛋白的氨基末端到第51个残基的DNA序列高度保守（95%同源性），并且没有氨基酸替代。（v）对应于羧基末端七个氨基酸残基的DNA序列只有42%的同源性，导致四个氨基酸替代。（vi）在大肠杆菌lpp基因中从终止密码子（UAA）开始并在寡聚（T）转录终止位点之前立即结束的40个碱基对区域内，有大约60%的同源性。然而，在这个区域之后，两个序列之间没有明显的同源性，可能是因为该区域有300个碱基对的缺失。（vii）在mRNA区域可以形成七个稳定的茎环结构。（viii）lpp基因中使用的密码子第三位的变化表明该基因的进化与粘质沙雷氏菌中的其他基因有所不同。
