Binding Affinity of Actinobacillus actinomycetemcomitans for extracellular matrix proteins

伴生放线杆菌是一种引起牙周发育和一些全身性疾病的病原菌。本研究考察了伴生放线杆菌与4种细胞外基质蛋白(I型胶原、IV型胶原、纤维连接蛋白和层粘连蛋白)的亲和力。放线菌伴生菌Y4和IDH781与固定化纤维连接蛋白和IV型胶原结合的能力强于I型胶原和层粘连蛋白。可溶性纤维连接蛋白和N型胶原抑制了细胞与固定化纤维连接蛋白和IV型胶原的结合，其中可溶性纤维连接蛋白与Y4和IDH781细胞提取的40 kDa蛋白结合，但不抑制可溶性IV型胶原结合。这些结果表明，伴放线放线杆菌Y4和IDH781与纤维连接蛋白具有较高的结合亲和力，这种结合可能受40 kDa细菌细胞蛋白的调节。Y4和IDH781也表现出对IV型胶原的高亲和力，细菌细胞的非蛋白成分可能参与了IV型胶原的结合。远缘链球菌产生的细胞表面蛋白抗原(PAg)和葡萄糖转移酶(GTF)是生物体的主要定植因子，抑制这两种因子可以预防龋病。在本研究中，我们构建了由PAg富含丙氨酸区和GTF葡聚糖结合区组成的融合蛋白(PAGA-GB)，并在兔体内制备了针对该融合蛋白的抗体。抗PagA-GB抗体显著抑制蔗糖依赖的黏附，但不抑制蔗糖非依赖性黏附。这些结果表明，抗GTF-I抗体可有效抑制远缘链霉菌的蔗糖依赖黏附。然而，S斑潜蝇的PAg可能不是主要作为获得性膜的受体，其他细胞表面蛋白可能参与了S斑潜蝇的非蔗糖非依赖性黏附。

Actinobacillus actinomycetemcomitans is an aetiologic agent in the development of periodontal and some systemic diseases in humans. In this study, the binding affinity of A. actinomycetemcomitans to 4 kinds of extracellular matrix protein (collagen type I, collagen type IV, fibronectin, and laminin) was investigated. A. actinomycetemcomitansY4 and IDH781 bound to immobilized fibronectin and collagen type IV more than collagen type I and laminin. The binding of the cells to immobilized fibronectin and type IV collagen was inhibited by both of soluble fibronectin and collagen type N. The soluble fibronectin, but not the soluble collagen type IV bound to the 40-kDa proteins that were extracted from Y4 and IDH781 cells. These results suggest that Actinobacillus actinomycetemcomitansY4 and IDH781 have high binding affinity for fibronectin and this binding may be regulated with the 40-kDa bacterial cell proteins. Y4 and IDH781 also showed high affinity for collagen type IV and the non-protein component of bacterial cells may be involved in binding to collagen type IV.The cell surface protein antigen (PAg) and glucosyltransferases (GTFs) produced by Streptococcus sobrinus are major colonization factors of the organism, and the inhibition of these two factors should provide protection against dental caries. In this study, we constructed a fusion protein (PAgA-GB) composed of the alanine-rich region of PAg and the glucan-binding domain of GTF, and the antibodies against the fusion protein were prepared in rabbits. The antibody against PAgA-GB significantly inhibited the sucrose-dependent adhesion, but not sucrose-independent adhesion. These results show that the antibody against GTF-I may be useful for effective inhibition of the sucrose-dependent adhesion of S. sobrinus. However, PAg of S sobrinus may not function primarily as a receptor for acquired pellicles, and other cell surface proteins may be involved in the sucrose-independent adhesion of S sobrinus.