Demuth D R, Lammey M S, Huck M, Lally E T, Malamud D
Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia 19104.
Microb Pathog. 1990 Sep;9(3):199-211. doi: 10.1016/0882-4010(90)90022-i.
Oral streptococci vary in their susceptibility to salivary agglutinin-mediated aggregation. To understand the molecular basis of this specificity, the structure and function of receptors for agglutinin from Streptococcus mutans KPSK2 (MSL-1) and Streptococcus sanguis M5 (SSP-5) were compared. Immunological screening of an S. mutans KPSK2 genomic DNA library yielded two identical clones expressing a streptococcal protein that co-migrated with a 220 kDa peptide in SDS extracts from this organism. This protein inhibited agglutinin-mediated aggregation of S. mutans KPSK2 in a dose-dependent manner. The MSL-1 gene is homologous to the S. mutans SpaP and pac genes although single base substitutions alter several amino acids. MSL-1 is also similar to the agglutinin receptor (SSP-5) cloned from S. sanguis M5. All three proteins, MSL-1, P1, and SSP-5 share at least one epitope since monoclonal and polyclonal anti-SSP-5 antibodies react with both MSL-1 and P1. However, other monoclonal antibodies are specific for SSP-5 and appear to react with a peptide domain exhibiting little homology to MSL-1 or P1. Sugar inhibition studies showed that agglutinin-mediated aggregation of S. mutans KPSK2 was most potently inhibited by fucose and lactose. Sialic acid, a potent inhibitor of S. sanguis aggregation, had no effect on the interaction of agglutinin with S. mutans KPSK2. These results suggest that while the MSL-1 and SSP-5 proteins are genetically and immunologically related, their specificity for binding sites on agglutinin differs.
口腔链球菌对唾液凝集素介导的聚集反应的敏感性各不相同。为了解这种特异性的分子基础，对变形链球菌KPSK2（MSL-1）和血链球菌M5（SSP-5）凝集素受体的结构和功能进行了比较。对变形链球菌KPSK2基因组DNA文库进行免疫筛选，得到了两个相同的克隆，它们表达一种链球菌蛋白，该蛋白在来自该菌株的SDS提取物中与一个220 kDa的肽段共迁移。这种蛋白以剂量依赖的方式抑制变形链球菌KPSK2的凝集素介导的聚集。MSL-1基因与变形链球菌SpaP和pac基因同源，尽管单碱基取代改变了几个氨基酸。MSL-1也与从血链球菌M5克隆的凝集素受体（SSP-5）相似。MSL-1、P1和SSP-5这三种蛋白至少有一个表位，因为单克隆和多克隆抗SSP-5抗体与MSL-1和P1都有反应。然而，其他单克隆抗体对SSP-5具有特异性，并且似乎与一个与MSL-1或P1几乎没有同源性的肽段结构域发生反应。糖抑制研究表明，岩藻糖和乳糖对变形链球菌KPSK2的凝集素介导的聚集有最强的抑制作用。唾液酸是血链球菌聚集的有效抑制剂，但对凝集素与变形链球菌KPSK2的相互作用没有影响。这些结果表明，虽然MSL-1和SSP-5蛋白在遗传和免疫方面相关，但它们对凝集素结合位点的特异性不同。
