Acyl chain specificity of the acyltransferases lpxA and lpxD and substrate availability contribute to lipid a fatty acid heterogeneity in Porphyromonas gingivalis
Acyl chain specificity of the acyltransferases lpxA and lpxD and substrate availability contribute to lipid a fatty acid heterogeneity in Porphyromonas gingivalis
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DOI：
10.1128/jb.00234-08
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Darveau, Richard P.
中科院分区：
文献类型：
--
作者：
Bainbridge, Brian W.;Karimi-Naser, Lisa;Darveau, Richard P.
牙龈卟啉单胞菌脂质A在脂肪酸的数量、类型和位置方面是异质的。通过基质辅助激光解吸电离-飞行时间质谱法分析脂质A揭示了不同的14个质量单位的峰簇，表明产生不同脂质A结构的脂肪酸的分布改变。为了研究具有不同链长的羟基脂肪酸的转移是否可以解释脂质A结构的聚集，牙龈卟啉单胞菌lpxA（lpxA（Pg））和lpxD（Pg）被克隆并在同源基因突变的大肠杆菌菌株中表达。发现来自表达牙龈卟啉单胞菌转移酶的菌株的脂质A除了正常的E. coli 14-碳羟基脂肪酸，表明这些酰基转移酶显示松弛的酰基链长度特异性。LpxA和LpxD均来自E.大肠杆菌或牙龈卟啉单胞菌在1%丙酸存在下生长时，也能够将奇数链脂肪酸掺入脂质A中。这表明E.大肠杆菌脂A酰基转移酶对14-碳羟基脂肪酸不具有绝对特异性，但如果脂肪酸底物可用，则可以转移相差一个碳单元的脂肪酸。我们得出结论，牙龈卟啉单胞菌脂质A酰基转移酶的松弛特异性和底物的可用性说明了牙龈卟啉单胞菌脂多糖制剂中观察到的14个质量单位不同的脂质A结构簇。
Porphyromonas gingivalis lipid A is heterogeneous with regard to the number, type, and placement of fatty acids. Analysis of lipid A by matrix-assisted laser desorption ionization-time of flight mass spectrometry reveals clusters of peaks differing by 14 mass units indicative of an altered distribution of the fatty acids generating different lipid A structures. To examine whether the transfer of hydroxy fatty acids with different chain lengths could account for the clustering of lipid A structures, P. gingivalis lpxA (lpxA(Pg)) and lpxD(Pg) were cloned and expressed in Escherichia coli strains in which the homologous gene was mutated. Lipid A from strains expressing either of the P. gingivalis transferases was found to contain 16-carbon hydroxy fatty acids in addition to the normal E. coli 14-carbon hydroxy fatty acids, demonstrating that these acyltransferases display a relaxed acyl chain length specificity. Both LpxA and LpxD, from either E. coli or P. gingivalis, were also able to incorporate odd-chain fatty acids into lipid A when grown in the presence of 1% propionic acid. This indicates that E. coli lipid A acyltransferases do not have an absolute specificity for 14-carbon hydroxy fatty acids but can transfer fatty acids differing by one carbon unit if the fatty acid substrates are available. We conclude that the relaxed specificity of the P. gingivalis lipid A acyltransferases and the substrate availability account for the lipid A structural clusters that differ by 14 mass units observed in P. gingivalis lipopolysaccharide preparations.