Structure-Based Design of Covalent Nanobody Binders for a Thermostable Green Fluorescence Protein

This is the authors' abstract. We don't add key points for this paper.

Green fluorescence protein (GFP) lights up almost every aspects of life sciences. An ultra thermostable GFP (TGP), engineered from a coral GFP, offers potential advantages over traditional jellyfish-derived GFP due to its high stability. However, owing to its later discovery, TGP lacks the extensive toolsets available for GFP, such as heavy chain-only antibody binders known as nanobodies. In this study, we have structurally characterized TGP in complex with Sb92, a synthetic nanobody identified from a previous in vitro screening, revealing its precise three-dimensional epitope. This structural insight, alongside the previously characterized Sb44-TGP complex, have allowed us to rationally design disulfide bonds between antigen and antibody for tighter interactions. Using biochemical analyses, we identify two bridged complexes (TGP A18C-Sb44 V100C, TGP E118C-Sb92 S57C), with the TGP-Sb92 disulfide pair showing high resistance to reducing agents. Our study expands the toolkit available for TGP and should encourage its wider applications.