Iovine Andrea, Filatov Andrei V, Kasimova Anastasiya A, Sharar Nowshin S, Ambrose Stephanie J, Dmitrenok Andrey S, Shneider Mikhail M, Shpirt Anna M, Perepelov Andrei V, Knirel Yuriy A, Hall Ruth M, De Castro Cristina, Kenyon Johanna J
Department of Chemical Sciences, University of Napoli Federico II Complesso Universitario Monte Santangelo, Via Cintia 4, I-80126, Naples, Italy.
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia; State Research Center Institute of Immunology, Federal Medical-Biological Agency of Russia, Moscow, Russia.
Carbohydr Res. 2025 Jan;547:109324. doi: 10.1016/j.carres.2024.109324. Epub 2024 Nov 19.
Capsular polysaccharide (CPS), a heteropolymeric carbohydrate structure present on the cell surface of most isolates of the bacterial pathogen Acinetobacter baumannii, is a major virulence determinant. Here, the CPS produced by A. baumannii MRSN 31468, which carries the KL58 CPS biosynthesis locus, was studied by sugar analysis, one- and two-dimensional H and C NMR spectroscopy. The structure was found to consist of a repeating tetrasaccharide K-unit that includes glucose (d-Glcp), galactose (d-Galp), N-acetyl-galactosamine (d-GalpNAc), and 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (5,7-di-N-acetylpseudaminic acid; Pse5Ac7Ac). The CPS has a branched repeating unit with the disaccharide →3)-β-d-Glc-(1→3)-β-d-GalNAc-(1→ as the mainchain and O-6 of the Glc unit substituted with the disaccharide β-Pse5Ac7Ac-(2→6)-α-d-Gal, and Pse5Ac7Ac is partially acetylated at O-4. The presence of Pse5Ac7Ac in the K58 structure is consistent with the presence of psaA-F genes in KL58, which are responsible for Pse5Ac7Ac synthesis. 4-O-acetylation of Pse5Ac7Ac was traced to an acetyltransferase, Atr44, which was found to be closely related to Atr29 that similarly decorates Pse5Ac7Ac with 4OAc in the K46-type CPS. Atr44 like Atr29 is encoded by a gene found in a prophage. The K58 CPS produced by MRSN 31468 did not include the 8-epimer of Pse5Ac7Ac (5,7-di-N-acetyl-8-epipseudaminic acid; 8ePse5Ac7Ac) found in the closely related CPS from BAL062 that also carries KL58. Hence, the gene(s) for conversion of Pse5Ac7Ac to 8ePse5Ac7Ac must lie elsewhere.
荚膜多糖（CPS）是一种存在于鲍曼不动杆菌大多数分离株细胞表面的杂聚碳水化合物结构，是主要的毒力决定因素。在此，对携带KL58 CPS生物合成位点的鲍曼不动杆菌MRSN 31468产生的CPS进行了糖分析、一维和二维氢谱及碳谱核磁共振光谱研究。发现该结构由一个重复的四糖K单元组成，其中包括葡萄糖（d - Glcp）、半乳糖（d - Galp）、N - 乙酰半乳糖胺（d - GalpNAc）和5,7 - 二乙酰氨基 - 3,5,7,9 - 四脱氧 - l - 甘油 - l - 甘露 - 壬 - 2 - 酮糖酸（5,7 - 二 - N - 乙酰假氨基糖酸；Pse5Ac7Ac）。该CPS具有一个分支重复单元，以二糖→3）-β - d - Glc -（1→3）-β - d - GalNAc -（1→为主链，Glc单元上的O - 6被二糖β - Pse5Ac7Ac -（2→6）-α - d - Gal取代，且Pse5Ac7Ac在O - 4处部分乙酰化。K58结构中Pse5Ac7Ac的存在与KL58中psaA - F基因的存在一致，这些基因负责Pse5Ac7Ac的合成。Pse5Ac7Ac的4 - O - 乙酰化归因于一种乙酰转移酶Atr44，发现它与Atr29密切相关，Atr29在K46型CPS中同样用4 - OAc修饰Pse5Ac7Ac。与Atr29一样，Atr44由一个前噬菌体中的基因编码。MRSN 31468产生的K58 CPS不包括在同样携带KL58的来自BAL062的密切相关CPS中发现的Pse5Ac7Ac的8 - 差向异构体（5,7 - 二 - N - 乙酰 - 8 - 表假氨基糖酸；8ePse5Ac7Ac）。因此，将Pse5Ac7Ac转化为8ePse5Ac7Ac的基因必定位于其他地方。
