Swartley J S, Balthazar J T, Coleman J, Shafer W M, Stephens D S
Emory University School of Medicine and VA Medical Center, Atlanta, Georgia 30033, USA.
Mol Microbiol. 1995 Nov;18(3):401-12. doi: 10.1111/j.1365-2958.1995.mmi_18030401.x.
Lysophosphatidic acid (LPA) acyltransferases of Neisseria meningitidis and Neisseria gonorrhoeae were identified which share homology with other prokaryotic and eukaryotic LPA acyltransferases. In Escherichia coli, the conversion of LPA to phosphatidic acid, performed by the 1-acyl-sn-glycerol-3-phosphate acyltransferase PlsC, is a critical intermediate step in the biosynthesis of membrane glycerophospholipids. A Tn916-generated mutant of a serogroup B meningococcal strain was identified that exhibited increased amounts of capsular polysaccharide, as shown by colony immunoblots, and a threefold increase in the number of assembled pili. The single, truncated 3.8 kb Tn916 insertion in the meningococcal mutant was localized within a 771 bp open reading frame, The gonococcal equivalent of this gene was identified by transformation with the cloned meningococcal mutant gene. In N. gonorrhoeae, the mutation increased piliation fivefold. The insertions were found to be within a gene that was subsequently designated nlaA (neisserial LPA acyltransferase). The predicted neisserial LPA acyltransferases were homologous (>20% identity, >40% amino acid similarity) to the family of PlsC protein homologues. A cloned copy of the meningococcal nlaA gene complemented in trans a temperature-sensitive E. coli PlsCts- mutant. Tn916 and omega-cassette insertional inactivations of the neisserial nlaA genes altered the membrane glycerophospholipid compositions of both N. meningitidis and N. gonorrhoeae but were not lethal. Therefore, the pathogenic Neisseria spp. appear to be able to utilize alternative enzyme(s) to produce phosphatidic acid. This hypothesis is supported by the observation that, although the amounts of mature glycerophospholipids were altered in the meningococcal and the gonococcal nlaA mutants, glycerophospholipid synthesis was detectable at significant levels. In addition, acyltransferase enzymatic activity, while reduced in the gonococcal nlaA mutant, was increased in the meningococcal nlaA mutant. We postulate that the pathogenic Neisseria spp. are able to utilize alternate acyltransferases to produce glycerophospholipids in the absence of nlaA enzymatic activity. Implementation of these secondary enzymes results in alterations of glycerophospholipid composition that lead to pleiotropic effects on the cell surface components, including effects on capsule and piliation.
已鉴定出脑膜炎奈瑟菌和淋病奈瑟菌的溶血磷脂酸（LPA）酰基转移酶，它们与其他原核和真核LPA酰基转移酶具有同源性。在大肠杆菌中，由1-酰基-sn-甘油-3-磷酸酰基转移酶PlsC将LPA转化为磷脂酸，这是膜甘油磷脂生物合成中的关键中间步骤。已鉴定出一株B群脑膜炎球菌菌株的Tn916诱导突变体，通过菌落免疫印迹显示其荚膜多糖含量增加，组装菌毛数量增加了三倍。脑膜炎球菌突变体中单个截短的3.8 kb Tn916插入片段定位于一个771 bp的开放阅读框内，通过用克隆的脑膜炎球菌突变基因进行转化鉴定出淋病奈瑟菌中的该基因等效物。在淋病奈瑟菌中，该突变使菌毛形成增加了五倍。发现插入片段位于一个随后被命名为nlaA（奈瑟菌LPA酰基转移酶）的基因内。预测的奈瑟菌LPA酰基转移酶与PlsC蛋白同源物家族同源（同一性>20%，氨基酸相似性>40%）。脑膜炎球菌nlaA基因的克隆拷贝可反式互补温度敏感型大肠杆菌PlsCts-突变体。奈瑟菌nlaA基因的Tn916和ω-盒插入失活改变了脑膜炎奈瑟菌和淋病奈瑟菌的膜甘油磷脂组成，但并不致命。因此，致病性奈瑟菌似乎能够利用替代酶来产生磷脂酸。这一假设得到以下观察结果的支持：尽管脑膜炎球菌和淋病奈瑟菌nlaA突变体中成熟甘油磷脂的含量发生了改变，但仍可检测到显著水平的甘油磷脂合成。此外，酰基转移酶的酶活性在淋病奈瑟菌nlaA突变体中降低，但在脑膜炎球菌nlaA突变体中增加。我们推测，致病性奈瑟菌在缺乏nlaA酶活性的情况下能够利用替代酰基转移酶来产生甘油磷脂。这些次生酶的作用导致甘油磷脂组成的改变，进而对细胞表面成分产生多效性影响，包括对荚膜和菌毛形成的影响。
