Probing the scalability of ultra stable catch bond complexes

The catch bond complex between serine-aspartate repeat protein G (SdrG) from Staphylococcus epidermidis and the beta chain of fibrinogen (Fg{beta}) exhibits two distinct rupture populations when dissociated under tensile force. Such complexes present exciting possibilities for developing dynamic biomaterials due to their unique response to shear force. However, the environmental responsiveness of this complex and its influence on adhesion behaviour in multi-valent systems remain underexplored. Using AFM-single molecule force spectroscopy (AFM-SMFS) and spinning disk adhesion (SDA) assays, we examined how protein orientation, mutations, and environment influence the stability and scaling behaviour of this catch bond system. Our findings confirmed that anchor point location (i.e., the direction from which the protein is pulled) strongly influences catch bond behaviour, while an S338H mutation in the binding domain destabilised the interaction in both single-molecule and multi-valent adhesion assays. This research examines how catch bond behaviour translates from the nanoscale to microscale using single molecule and multi-valent cell adhesion measurements and provides a toolkit for exploiting catch bonds towards macroscale material applications.