Streptococcus pneumoniae (the pneumococcus) has wall teichoic acid (WTA) and lipoteichoic acid (LTA) expressing the Forssman antigen (FA). Two lectins, Dolichos biflorus agglutinin (DBA) and Helix pomatia agglutinin (HPA), are known to bind FA. To determine the molecular structure targeted by these two lectins, different pneumococcal strains were studied for DBA/HPA binding with flow cytometry and fluorescence microscopy. Genetic experiments were used to further examine the lectins’ molecular target. Twelve strains were positive for DBA binding, whereas three were negative. Super‐resolution microscopy showed that DBA stained only the subcapsular area of pneumococci. The three DBA nonbinders showed no phosphorylcholine esterase (Pce) activity in vitro, whereas 10 DBA binders displayed Pce activity (the remaining two strains were DBA binders with no Pce activity in vitro). The pcegene sequence for 10 representative strains revealed two functional pce alleles, the previously recognized “allele A” and a newly discovered “allele B” (with 12 additional nucleotides). Isolates with allele B showed no Pce activity in vitro but did bind to DBA, indicating allele B Pce is functional in vivo. Genetic transfer experiments confirmed that either allele is sufficient (and necessary) for DBA binding. The three DBA nonbinders had various mutations that affected Pce function. Observations with HPA were identical to those with DBA. We show that DBA and HPA bind only to the WTA/LTA of pneumococcal isolates with a functional Pce enzyme. A newly discovered Pce variant (allele B) is functional in vivo but nonfunctional when assayed in vitro.

中文翻译：

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磷酰胆碱酯酶对于双花多利果和螺旋藻凝集素与肺炎球菌磷壁酸的结合至关重要。

肺炎链球菌（肺炎球菌）具有表达 Forssman 抗原 (FA) 的壁磷壁酸 (WTA) 和脂磷壁酸 (LTA)。两种凝集素，Dolichos biflorus凝集素 (DBA) 和Helix pomatia已知凝集素 (HPA) 与 FA 结合。为了确定这两种凝集素靶向的分子结构，使用流式细胞术和荧光显微镜研究了不同肺炎球菌菌株的 DBA/HPA 结合。遗传实验用于进一步检查凝集素的分子靶标。十二株对 DBA 结合呈阳性，而三株为阴性。超分辨率显微镜显示 DBA 仅染色肺炎球菌的包膜下区域。三种 DBA 非结合剂在体外没有表现出磷酸胆碱酯酶 (Pce) 活性，而 10 种 DBA 结合剂显示出 Pce 活性（其余两种菌株是在体外没有 Pce 活性的 DBA 结合剂）。10 个代表性菌株的pce基因序列揭示了两个功能性pce等位基因，先前识别的“等位基因 A”和新发现的“等位基因 B”（具有 12 个额外的核苷酸）。具有等位基因 B 的分离株在体外没有表现出 Pce 活性，但确实与 DBA 结合，表明等位基因 B Pce 在体内是有功能的。遗传转移实验证实，任一等位基因对于 DBA 结合都是足够的（并且是必要的）。三个 DBA 非结合物具有影响 Pce 功能的各种突变。HPA 的观察结果与 DBA 的观察结果相同。我们表明 DBA 和 HPA 仅与具有功能性 Pce 酶的肺炎球菌分离株的 WTA/LTA ​​结合。新发现的 Pce 变体（等位基因 B）在体内有功能，但在体外检测时无功能。