Department of Microbiology and Oral Infection, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Department of Oral Microbiology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
Mol Oral Microbiol. 2018 Feb;33(1):68-80. doi: 10.1111/omi.12200. Epub 2017 Nov 17.
Porphyromonas gingivalis can synthesize both A-LPS and O-LPS lipopolysaccharides, which contain anionic O-polysaccharides and conventional O-polysaccharides, respectively. A-LPS can anchor virulence proteins to the cell surface, so elucidating the mechanism of A-LPS synthesis is important for understanding the pathogenicity of this bacterium. To identify the genes involved in LPS synthesis, we focused on uncharacterized genes encoding the glycosyltransferases, PGN_0361, PGN_1239, PGN_1240 and PGN_1668, which were tentatively named gtfC, gtfD, gtfE and gtfF, respectively, and characterized their mutants. We found that disruption of gtfC and gtfF resulted in A-LPS deficiency. In addition, a gtfD mutant had abnormal A-LPS synthesis, and a gtfE mutant exhibited a rough-type LPS that possesses a short oligosaccharide with lipid A-core. We then constructed a gtfC and gtfD double mutant, because their amino acid sequences were very similar, and this mutant similarly possessed a rough-type LPS. Cross-complementation analysis revealed that the GtfD protein is a functional homologue of the Escherichia coli WbbL protein, which is a rhamnosyltransferase. These results suggested that the GtfE protein is essential for the synthesis of both O-LPS and A-LPS, and that GtfC and GtfD proteins may work together to synthesize the two kinds of LPS. In addition, the GtfF protein was essential for A-LPS synthesis, although this may be achieved in a strain-specific manner.
牙龈卟啉单胞菌可以合成 A-LPS 和 O-LPS 脂多糖，它们分别含有阴离子 O-多糖和常规 O-多糖。A-LPS 可以将毒力蛋白锚定在细胞表面，因此阐明 A-LPS 合成的机制对于理解该细菌的致病性非常重要。为了鉴定 LPS 合成相关的基因，我们重点研究了未鉴定功能的基因，这些基因编码糖基转移酶，PGN_0361、PGN_1239、PGN_1240 和 PGN_1668，它们分别被暂定命名为 gtfC、gtfD、gtfE 和 gtfF，并对它们的突变体进行了表征。我们发现 gtfC 和 gtfF 的缺失导致 A-LPS 缺失。此外，gtfD 突变体的 A-LPS 合成异常，gtfE 突变体表现出粗糙型 LPS，其具有带有脂质 A 核心的短寡糖。然后，我们构建了 gtfC 和 gtfD 双突变体，因为它们的氨基酸序列非常相似，该突变体也具有粗糙型 LPS。交叉互补分析表明，GtfD 蛋白是大肠杆菌 WbbL 蛋白的功能同源物，WbbL 蛋白是一种鼠李糖基转移酶。这些结果表明，GtfE 蛋白对于 O-LPS 和 A-LPS 的合成都是必需的，而 GtfC 和 GtfD 蛋白可能共同参与两种 LPS 的合成。此外，尽管 GtfF 蛋白可能以菌株特异性的方式参与 A-LPS 的合成，但它对于 A-LPS 合成是必需的。
