Surface proteins, such as AgⅠ/Ⅱ , P1, PAc, SpaP, SspA, and SspB, are widely observed in oral Streptococcus. These proteins mediate the attachment of Streptococcus mutans, Streptococcus sobrinus, Streptococcus gordonii, and so on to tooth surfaces, influence the formation of dental plaque, and are the main virulent factors for the development of caries diseases. The crystal structure of region V of AgⅠ/Ⅱ (SpaP-V) was first studied, after which research on the 3D structures of the full-length AgⅠ/Ⅱ as well as regions V and C of SspB was performed. The 3D structures of AgⅠ/Ⅱ were also gradually elucidated to better explain the mechanism of function of the proteins. Research advances on the 3D structure of Ag Ⅰ/Ⅱ and the related functional epitopes are finally reviewed.
