In molecular self-assembly, molecules, or parts of molecules, spontaneously form ordered structures without external factors. Macromolecular assemblies consist of multiple proteins and often, other molecules such as DNA, RNA, sugars and/or lipids. The assembly of macromolecular complexes in a cell is a highly regulated multistep process.
Mass photometry allows the characterisation of these complex particles with efficiency and accuracy, enabling the engineering of new supramolecular structures with great potential in medicine.
GroEL is a 14-mer, cage-like complex, which assists the correct folding and assembly of other proteins in the cell. Formation of this complex was monitored using mass photometry, under different buffer conditions.
Ribosomes are macromolecular assemblies of protein and RNA that are the central sites for protein synthesis. Bacterial ribosomes ((E.coli in this example) are >2 MDa in size. Magnesium plays subtle, yet important, roles in the assembly of these complexes. In the absence of magnesium, the ribosomes rapidly disassemble into two subunits, which can be monitored with mass photometry.
Adeno-associated virus (AAV) is one of the most actively investigated gene therapy vehicles. In the presented example mass photometry resolved empty (~3.7 MDa) and DNA loaded capsids (~1 MDa shift).
An ultra-stable gold-coordinated protein cage displaying reversible assembly
Malay at al., Nature 2019, 569(7756), 438-442
Cage-like protein assemblies have potential uses in medicine, including as vaccines and in drug delivery. In this study, mass photometry was used to follow formation of a TRAP-cage. It showed that a critical concentration of TRAP is required for effective cage formation. Above this critical concentration, the TRAP rings appear to rapidly assemble into an intermediate, partially formed cage, with the cage then forming from this intermediate.