Cell surface‐localized P1 adhesin (aka Antigen I/II or PAc) of the cariogenic bacterium Streptococcus mutans mediates sucrose‐independent adhesion to tooth surfaces. Previous studies showed that P1’s C‐terminal segment (C123, AgII) is also liberated as a separate polypeptide, contributes to cellular adhesion, interacts specifically with intact P1 on the cell surface, and forms amyloid fibrils. Identifying how C123 specifically interacts with P1 at the atomic level is essential for understanding related virulence properties of S. mutans. However, with sizes of ~ 51 and ~ 185 kDa, respectively, C123 and full‐length P1 are too large to achieve high‐resolution data for full structural analysis by NMR. Here, we report on biologically relevant interactions of the individual C3 domain with A3VP1, a polypeptide that represents the apical head of P1 as it is projected on the cell surface. Also evaluated are C3’s interaction with C12 and the adhesion‐inhibiting monoclonal antibody (MAb) 6‐8C. NMR titration experiments with 15N‐enriched C3 demonstrate its specific binding to A3VP1. Based on resolved C3 assignments, two binding sites, proximal and distal, are identified. Complementary NMR titration of A3VP1 with a C3/C12 complex suggests that binding of A3VP1 occurs on the distal C3 binding site, while the proximal site is occupied by C12. The MAb 6‐8C binding interface to C3 overlaps with that of A3VP1 at the distal site. Together, these results identify a specific C3‐A3VP1 interaction that serves as a foundation for understanding the interaction of C123 with P1 on the bacterial surface and the related biological processes that stem from this interaction.
Database
BMRB submission code: 27935.
stem-loop. These modifications affect other aspects of translation such as the ability of the ribosome to maintain the three-nucleotide codon of the mRNA as it moves through the ribosome. The absolute requirement for precise correlation between the mRNA frame and the correct protein sequence to be expressed underlies an fundamental question in molecular biology: what regulates the mRNA reading frame? To address this question, we study defined biological systems that subvert the three-nucleotide mRNA reading frame resulting in high levels of frameshifting. Our biochemical and structural results reveal that tRNA distortion and conformational changes of the small ribosomal subunit are induced by frameshift-prone tRNAs. This dysregulation causes the ribosome to lose its grip on the mRNA, allowing the tRNA to shift into a new reading frame. Together these studies reveal how the ribosome undergoes recoding into alternative mRNA frames and suggests how dysregulation of the mRNA frame disrupts key interactions between tRNAs, mRNA, and translation factors with the ribosome.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.