In nature, proteins self-assemble into various structures with different dimensions. To construct these nanostructures in laboratories, normally proteins with different symmetries are selected. However, most of these approaches are engineering-intensive and highly dependent on the accuracy of the protein design. Herein, we report that a simple native protein LecA assembles into one-dimensional nanoribbons and nanowires, two-dimensional nanosheets, and three-dimensional layered structures controlled mainly by small-molecule assembly-inducing ligands RnG (n=1, 2, 3, 4, 5) with varying numbers of ethylene oxide repeating units. To understand the formation mechanism of the different morphologies controlled by the small-molecule structure, molecular simulations were performed from microscopic and mesoscopic view, which presented a clear relationship between the molecular structure of the ligands and the assembled patterns. These results introduce an easy strategy to control the assembly structure and dimension, which could shed light on controlled protein assembly.

Red fluorescent proteins (RFPs) are powerful tools used in molecular biology research. Although RFP can be easily monitored in vivo, manipulation of RFP by suitable nanobodies binding to different epitopes of RFP is still desired. Thus, it is crucial to obtain structural information on how the different nanobodies interact with RFP. Here, we determined the crystal structures of the LaM2‐mCherry and LaM4‐mCherry complexes at 1.4 and 1.9 Å resolution. Our results showed that LaM2 binds to the side of the mCherry β‐barrel, while LaM4 binds to the bottom of the β‐barrel. The distinct binding sites of LaM2 and LaM4 were further verified by isothermal titration calorimetry, fluorescence‐based size exclusion chromatography, and dynamic light scattering assays. Mutation of the residues at the LaM2 or LaM4 binding interface to mCherry significantly decreased the binding affinity of the nanobody to mCherry. Our results also showed that LaM2 and LaM4 can bind to mCherry simultaneously, which is crucial for recruiting multiple operation elements to the RFP. The binding of LaM2 or LaM4 did not significantly change the chromophore environment of mCherry, which is important for fluorescence quantification assays, while several GFP nanobodies significantly altered the fluorescence. Our results provide atomic resolution interaction information on the binding of nanobodies LaM2 and LaM4 with mCherry, which is important for developing detection and manipulation methods for RFP‐based biotechnology.

We introduced a small molecular “inducing ligand” strategy to crystallize proteins via dual noncovalent interactions. Here we demonstrate that the variant protein-packing frameworks of concanavalin A (ConA) binding with ligands are controlled by different crystallization methods. Besides, the protein crystalline frameworks are also controlled by small-molecule inducing ligands R n M (n = 1–5), which varies in the number of ethylene oxide repeating units. To better understand the mechanism of different packing frameworks controlled by different inducing ligands, all-atom molecular dynamic (MD) simulations were performed. The MD simulation focused on the dynamic dimerization behavior of ConA-R n M system, which revealed clear relationships between the length of inducing ligands and ConA crystalline. In short, besides protein-packing framework control via different crystallization methods, inducing ligands R n M with suitable spacer lengths (n = 3, 4) also play an important role in desired and stable crystalline frameworks.

In nature, proteins self‐assemble into various structures with different dimensions. To construct these nanostructures in laboratories, normally proteins with different symmetries are selected. However, most of these approaches are engineering‐intensive and highly dependent on the accuracy of the protein design. Herein, we report that a simple native protein LecA assembles into one‐dimensional nanoribbons and nanowires, two‐dimensional nanosheets, and three‐dimensional layered structures controlled mainly by small‐molecule assembly‐inducing ligands RnG (n=1, 2, 3, 4, 5) with varying numbers of ethylene oxide repeating units. To understand the formation mechanism of the different morphologies controlled by the small‐molecule structure, molecular simulations were performed from microscopic and mesoscopic view, which presented a clear relationship between the molecular structure of the ligands and the assembled patterns. These results introduce an easy strategy to control the assembly structure and dimension, which could shed light on controlled protein assembly.

Red fluorescent proteins (RFPs) are widely used in molecular biology research, especially in deep tissues and animal models, because of their superior autofluorescence, light scattering, and phototoxicity to GFP. Although RFP can be easily monitored in vivo, improved manipulation of RFP is still desired. Using suitable nanobodies (Nbs) to bind to different epitopes of RFP is the most promising approach; thus, it is crucial to obtain structural information on how the different Nbs interact with RFP. We determined the crystal structures of the LaM2-mCherry and LaM4-mCherry complexes at 1.4 Å and 1.9 Å resolution. Our results showed that LaM2 binds to the side of the mCherry β-barrel, while Lam4 binds to the bottom of the β-barrel and does not interfere with the homo-oligomerization interface. The distinct binding sites of LaM2 and LaM4 were further verified by ITC, F-SEC and DLS assays. Our results also showed that LaM2 and LaM4 can bind simultaneously to mCherry, which is crucial for recruiting multiple operation elements to the RFP. The binding of LaM2 or LaM4 did not significantly change the chromophore environment of mCherry, which is important for fluorescence quantification assays, while several GFP Nbs significantly altered the fluorescence. Mutation of the residues of the LaM2 or LaM4 binding interface to mCherry significantly decreased the binding affinity of the Nb to mCherry. Our results provided atomic resolution interaction information on the binding of Nbs LaM2 and LaM4 binding with mCherry, which is important for developing detection and manipulation methods for RFP-based biotechnology.