Methodology development: putting enzymes on DNA scaffold.
In nature, the catalytic efficiency of multienzyme complexes highly depends on their spatial organization. The positions and orientations of the composite enzymes are often precisely controlled to facilitate substrate transport between them. Self-assembled DNA nanostructures hold great promise for organizing biomolecules at the nanoscale. Here, we present detailed protocols for exploiting DNA nanostructures as assembly scaffolds that organize the spatial arrangements of multienzyme cascades with control over their relative distance, compartmentalization and substrate diffusion paths. The protocol describes the preparation and purification of DNA-conjugated enzymes and cofactors, along with the assembly of these prepared complexes on DNA nanostructures. The architecture of assembled enzyme complexes is then readily characterized using a broad selection of techniques from routine gel electrophoresis to advanced single-molecule imaging. We also describe methods of purifying these nano-assemblies and testing them with functional assays based on either bulk or single-molecule fluorescence measurements. The entire assembly and characterization of a multienzyme complex can be completed within 1–2 weeks.
An Artificial Swinging arm on DNA nanoscaffold.
Swinging arms are a key functional component of multistep catalytic transformations in many naturally occurring multi-enzyme complexes1. This arm is typically a prosthetic chemical group that is covalently attached to the enzyme complex via a flexible linker, allowing the direct transfer of substrate molecules between multiple active sites within the complex. Mimicking this method of substrate channelling outside the cellular environment requires precise control over the spatial parameters of the individual components within the assembled complex. DNA nanostructures can be used to organize functional molecules with nanoscale precision and can also provide nanomechanical control. Until now, protein–DNA assemblies have been used to organize cascades of enzymatic reactions by controlling the relative distance and orientation of enzymatic components or by facilitating the interface between enzymes/cofactors and electrode surfaces. Here, we show that a DNA nanostructure can be used to create a multi-enzyme complex in which an artificial swinging arm facilitates hydride transfer between two coupled dehydrogenases. By exploiting the programmability of DNA nanostructures, key parameters including position, stoichiometry and inter-enzyme distance can be manipulated for optimal activity.
Gaining momentum by swinging arms.
We assembled an artificial 2D enzyme network of two related dehydrogenase enzymes on a wireframe DNA origami template to facilitate swinging of the redox intermediate substrate to enhance enzyme cascade activity. The 2D organized enzyme system exhibited higher reaction efficiency than single enzyme pairs due to promoted transfer of intermediates within the network.
CryoEM structure reveals detailed immune responses.
HIV vaccine development has been A glycan hole is one of the most dominant autologous neutralizing epitopes targeted on BG505 and B41 SOSIP trimer-immunized rabbits. Our high-resolution cryo-electron microscopy (cryoEM) studies of B41 in complex with a B41-specific antibody complex elucidate the molecular basis of this strain-specific glycan hole response. We conclude that even for the immunodominant glycan hole shared between BG505 and B41, the prospect of designing prime-boost immunogens remains difficult.