Infections caused by Acinetobacter baumannii isolates from the major global clones, GC1 and GC2, are difficult to treat with antibiotics, and phage therapy, which requires extensive knowledge of the variation in the surface polysaccharides, is an option under consideration. The gene clusters directing the synthesis of capsular polysaccharide (CPS) in A. baumannii GC1 isolate A388 and GC2 isolate G21 differ by a single glycosyltransferase (gtr) gene. They include genes encoding a novel UDP-glucose dehydrogenase (Ugd2) and a putative pyruvyl transferase (Ptr2). The composition and structures of the linear K20 and K21 tetrasaccharide repeats (K units) of the CPSs isolated from A338 and G21, respectively, were established by sugar analyses and Smith degradation along with 1D and 2D ¹H and ¹³C NMR spectroscopy. The K20 and K21 CPSs are the first known to include GlcpA produced by Ugd2 and d-galactose with an (R)-configured 4,6-pyruvic acid acetal added by Prt2. The first sugar in the tetrasaccharide K units is 2-acetamido-4-amino-2,4,6-trideoxy-d-glucose (d-QuipNAc4N) that carries a 4-N-[(S)-3-hydroxybutanoyl] group in some K units and a 4-N-acetyl group in the others. Accordingly, K unit polymerases Wzy_K20 and Wzy_K21 form a β-d-QuipNAc4NR-(1→2)-d-Galp bond. The K20 and K21 units differ only in the configuration of the glycosidic linkages of d-GlcpNAc allowing the unique inverting glycosyltransferases Gtr43 and the retaining glycosyltransferase Gtr45 to be assigned to the formation of the β-d-GlcpNAc-(1→4)-d-GlcpA and α-d-GlcpNAc-(1→4)-d-GlcpA linkages, respectively.

中文翻译：

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鲍曼不动杆菌K20和K21荚膜多糖结构确立了UDP-葡萄糖脱氢酶Ugd2，丙酮基转移酶Ptr2和两个糖基转移酶的作用

来自全球主要主要克隆GC1和GC2的鲍曼不动杆菌分离株引起的感染很难用抗生素治疗，噬菌体治疗需要对表面多糖的变化有广泛的了解，这是正在考虑的一种选择。鲍曼不动杆菌GC1分离物A388和GC2分离物G21中指导荚膜多糖（CPS）合成的基因簇的区别在于单个糖基转移酶（gtr）基因。它们包括编码新型UDP-葡萄糖脱氢酶（Ugd2）和推定的丙酮基转移酶（Ptr2）的基因。分别通过糖分析和Smith降解以及1D和2D ¹ H和¹³ C NMR光谱确定分别从A338和G21分离的CPS的线性K20和K21四糖重复序列（K单位）的组成和结构。K20和K21 CPS是第一个已知的化合物，包括由Ugd2生产的Glc p A和d-半乳糖，以及由Prt2添加的（R）-构型的4,6-丙酮酸缩醛。在四糖K为单位的第一种糖是2-乙酰氨基-4-氨基-2,4,6-三脱氧D-葡萄糖（d -Qui pNAc4N）在一些K单元中带有一个4-N-[（S）-3-羟基丁酰基]基，在其他K个单元中带有一个4-N-乙酰基。因此，K单元聚合酶WZY _K20和WZY _K21形式的β- d -Qui p NAc4NR-（1→2） - d -Gal p键。K20和K21单元的区别仅在于d -Glc p NAc的糖苷键的构型不同，从而可以将独特的反向糖基转移酶Gtr43和保留的糖基转移酶Gtr45分配给β- d -Glc p NAc-（1→ 4）-d -Glc p A和α- d -Glcp NAc-（1→4）-d -Glc p A键。