Binding Affinity of Actinobacillus actinomycetemcomitans for extracellular matrix proteins

伴放线放线杆菌是引起人类牙周及某些系统性疾病的病原菌。在本研究中，A.研究了放线菌共生菌对4种细胞外基质蛋白（I型胶原、IV型胶原、纤连蛋白和层粘连蛋白）的作用。A.放线菌共生菌Y 4和IDH 781与固定化纤连蛋白和IV型胶原的结合能力强于I型胶原和层粘连蛋白。可溶性纤连蛋白和N型胶原均能抑制细胞与固定化纤连蛋白和IV型胶原的结合。可溶性纤连蛋白，但不是可溶性IV型胶原结合到从Y 4和IDH 781细胞提取的40-kDa蛋白质。这些结果表明放线共生放线杆菌Y 4和IDH 781对纤连蛋白具有高的结合亲和力，并且这种结合可能受40-kDa细菌细胞蛋白的调节。Y 4和IDH 781也显示出对IV型胶原的高亲和力，并且细菌细胞的非蛋白组分可能参与与IV型胶原的结合。远缘链球菌产生的细胞表面蛋白抗原（PAg）和葡萄糖基转移酶（GTF）是生物体的主要定植因子，并且这两个因子的抑制应该提供对龋齿的保护。在本研究中，我们构建了由PAg的富含丙氨酸的区域和GTF的葡聚糖结合结构域组成的融合蛋白（PAgA-GB），并在兔体内制备了针对该融合蛋白的抗体。抗PAgA-GB的抗体显著抑制蔗糖依赖性粘附，但不抑制蔗糖非依赖性粘附。这些结果表明，抗GTF-1的抗体可用于有效抑制S. sobrinus。然而，Ssobrinus的PAg可能不主要作为获得性表膜的受体发挥作用，并且其他细胞表面蛋白可能参与Ssobrinus的蔗糖非依赖性粘附。

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.