MOLECULAR CHARACTERIZATION OF ENTEROBACTERIAL PLDA GENES ENCODING OUTER-MEMBRANE PHOSPHOLIPASE-A
MOLECULAR CHARACTERIZATION OF ENTEROBACTERIAL PLDA GENES ENCODING OUTER-MEMBRANE PHOSPHOLIPASE-A
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DOI：
10.1128/jb.176.3.861-870.1994
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发表时间：
1994-02-01
影响因子：
3.2
通讯作者：
TOMMASSEN, J
中科院分区：
文献类型：
--
作者：
BROK, RGPM;BRINKMAN, E;TOMMASSEN, J
大肠杆菌的pldA基因编码外膜磷脂酶A。携带最常用的突变体pldA等位基因的菌株似乎在外膜中表达正确组装的PldA蛋白。核苷酸序列分析表明，野生型和突变体之间的唯一区别是在位置152处的丝氨酸残基被苯丙氨酸取代。由于缺乏pldA基因的突变体在实验室条件下正常存活，并且除了缺乏外膜磷脂酶活性外没有明显的表型，因此该酶的确切作用仍然未知。尽管如此，这种酶似乎对细菌很重要，因为蛋白质印迹法（免疫印迹法）和酶测定表明它在肠杆菌科物种中广泛传播。为了进一步表征PldA蛋白，对鼠伤寒沙门氏菌、肺炎克雷伯氏菌和普通变形杆菌的pldA基因进行克隆和测序。克隆的基因在E.大肠杆菌中表达，表达产物具有酶活性。预测的PldA一级结构与E. coliPldA显示出高度的同源性，在所有四种蛋白中79%的氨基酸残基是相同的。讨论了序列比较对PldA蛋白结构和结构-功能关系的意义。
The pldA gene of Escherichia coli encodes an outer membrane phospholipase A. A strain carrying the most commonly used mutant pldA allele appeared to express a correctly assembled PldA protein in the outer membrane. Nucleotide sequence analysis revealed that the only difference between the wild type and the mutant is the replacement of the serine residue in position 152 by phenylalanine. Since mutants that lack the pldA gene were normally viable under laboratory conditions and had no apparent phenotype except for the lack of outer membrane phospholipase activity, the exact role of the enzyme remains unknown. Nevertheless, the enzyme seems to be important for the bacteria, since Western blotting (immunoblotting) and enzyme assays showed that it is widely spread among species of the family Enterobacteriaceae. To characterize the PldA protein further, the pldA genes of Salmonella typhimurium, Klebsiella pneumoniae, and Proteus vulgaris were cloned and sequenced. The cloned genes were expressed in E. coli, and their gene products were enzymatically active. Comparison of the predicted PldA primary structures with that of E. coli PldA revealed a high degree of homology, with 79% of the amino acid residues being identical in all four proteins. Implications of the sequence comparison for the structure and the structure-function relationship of PldA protein are discussed.