The Role of Proline Isomerization as a Route for Opa-CEACAM Specificity

Due to the prevalence of antibiotic use in recent decades, there has been a rise in antibiotic resistant bacterial infections. Bacterial gonorrhea is one such infection and the responsible bacterium, Neisseria gonorrhoeae, has reached superbug status with strains that are resistant to all available antibiotics. Neisseria triggers uptake by human cells by binding to carcinoembryonic antigen-like cell adhesion molecules (CEACAMs) on the surface of host cells via opacity associated proteins (Opa) located in the outer membrane of Neisseria. Opa proteins are eight-stranded β-barrel proteins that have four extracellular loops. Extracellular loops two and three contain hypervariable regions. These hypervariable regions are responsible for the binding specificity between Opa and the N-terminal Ig-like V-domain conserved across all CEACAMs. Opa60, an Opa protein expressed in N. gonorrhoeae, binds CEACAM1, 3, 5, and 6. While it is established that Opa proteins bind the N-terminal domain in CEACAM1, the molecular determinants of binding specificity remain unknown. This study will investigate the role of proline isomerization in Opa60 using mutagenesis studies, solution NMR and in vitro binding assays.