Ernst Robert K, Adams Kristin N, Moskowitz Samuel M, Kraig Gretchen M, Kawasaki Kiyoshi, Stead Christopher M, Trent M Stephen, Miller Samuel I
Department of Medicine, University of Washington, HSB T-293, Box 357710, 1959 Pacific Street N.E., Seattle, WA 98195, USA.
J Bacteriol. 2006 Jan;188(1):191-201. doi: 10.1128/JB.188.1.191-201.2006.
Lipopolysaccharide (LPS) is the major surface component of gram-negative bacteria, and a component of LPS, lipid A, is recognized by the innate immune system through the Toll-like receptor 4/MD-2 complex. Pseudomonas aeruginosa, an environmental gram-negative bacterium that opportunistically infects the respiratory tracts of patients with cystic fibrosis (CF), can synthesize various structures of lipid A. Lipid A from P. aeruginosa strains isolated from infants with CF has a specific structure that includes the removal of the 3 position 3-OH C10 fatty acid. Here we demonstrate increased expression of the P. aeruginosa lipid A 3-O-deacylase (PagL) in isolates from CF infants compared to that in environmental isolates. PagL activity was increased in environmental isolates by growth in medium limited for magnesium and decreased by growth at low temperature in laboratory-adapted strains of P. aeruginosa. P. aeruginosa PagL was shown to be an outer membrane protein by isopycnic density gradient centrifugation. Heterologous expression of P. aeruginosa pagL in Salmonella enterica serovar Typhimurium and Escherichia coli resulted in removal of the 3-OH C14 fatty acid from lipid A, indicating that P. aeruginosa PagL recognizes either 3-OH C10 or 3-OH C14. Finally, deacylated lipid A species were not observed in some clinical P. aeruginosa isolates from patients with severe pulmonary disease, suggesting that loss of PagL function can occur during long-term adaptation to the CF airway.
脂多糖（LPS）是革兰氏阴性菌的主要表面成分，LPS的一个组成部分脂质A通过Toll样受体4/MD-2复合物被天然免疫系统识别。铜绿假单胞菌是一种环境革兰氏阴性菌，可机会性感染囊性纤维化（CF）患者的呼吸道，它能合成多种结构的脂质A。从CF婴儿分离出的铜绿假单胞菌菌株的脂质A具有特定结构，包括去除3位的3-OH C10脂肪酸。在此我们证明，与环境分离株相比，来自CF婴儿的分离株中铜绿假单胞菌脂质A 3-O-脱酰酶（PagL）的表达增加。在镁受限的培养基中生长，环境分离株中的PagL活性增加，而在实验室适应的铜绿假单胞菌菌株中，低温生长则使其活性降低。通过等密度梯度离心显示，铜绿假单胞菌PagL是一种外膜蛋白。铜绿假单胞菌pagL在鼠伤寒沙门氏菌和大肠杆菌中的异源表达导致脂质A中的3-OH C14脂肪酸被去除，这表明铜绿假单胞菌PagL可识别3-OH C10或3-OH C14。最后，在一些患有严重肺部疾病患者的临床铜绿假单胞菌分离株中未观察到去酰化脂质A种类，这表明在长期适应CF气道过程中可能会发生PagL功能丧失。
