Bouvier J, Pugsley A P, Stragier P
Institut de Microbiologie, Bâtiment 409, Université Paris-Sud, France.
J Bacteriol. 1991 Sep;173(17):5523-31. doi: 10.1128/jb.173.17.5523-5531.1991.
Cloning and sequence analysis of the region located downstream of the dapA gene of Escherichia coli has revealed the presence of an open reading frame that is cotranscribed with dapA. This gene codes for a 344-amino-acid polypeptide with a potential signal sequence characteristic of a lipoprotein. When this gene, called nlpB, is expressed from a multicopy plasmid in bacteria grown in the presence of [3H]palmitate, a labeled 37-kDa protein is produced. A slightly larger precursor molecule is detected when minicells expressing nlpB are treated with globomycin, a specific inhibitor of lipoprotein signal peptidase. Therefore, the nlpB gene encodes a new lipoprotein, designated NlpB. This lipoprotein is detected in outer membrane vesicles prepared from osmotically lysed spheroplasts and appears to be nonessential, since a strain in which the nlpB gene is disrupted by insertion of a chloramphenicol resistance gene is still able to grow and shows no discernible NlpB phenotype. The putative transcription termination signals of the dapA-nlpB operon overlap the promoter of the adjacent purC gene.
对大肠杆菌dapA基因下游区域的克隆及序列分析表明，存在一个与dapA共转录的开放阅读框。该基因编码一个含有344个氨基酸的多肽，具有脂蛋白潜在信号序列的特征。当这个名为nlpB的基因在含有[3H]棕榈酸的条件下从多拷贝质粒在细菌中表达时，会产生一种标记的37 kDa蛋白。当用脂蛋白信号肽酶的特异性抑制剂球状霉素处理表达nlpB的微小细胞时，会检测到一个稍大的前体分子。因此，nlpB基因编码一种新的脂蛋白，命名为NlpB。这种脂蛋白在由渗透裂解的原生质体制备的外膜囊泡中被检测到，并且似乎是非必需的，因为一个nlpB基因被氯霉素抗性基因插入破坏的菌株仍然能够生长，并且没有明显的NlpB表型。dapA-nlpB操纵子的推定转录终止信号与相邻purC基因的启动子重叠。
