Multihexamers

Multihexamers are supramolecular assemblies formed by the association of two or more hexameric subunits or hexameric building blocks. They can be composed of identical hexamers (homomeric) or of different hexamer types (heteromeric) and are common in biology as higher-order platforms for catalysis, transport, or structural support.

Architecturally, multihexamers typically exhibit defined symmetry and interfaces between neighboring hexamers that stabilize the assembly. The geometry can range from two-dimensional lattices and tubular arrays to three-dimensional shells or capsid-like particles. The precise arrangement is determined by protein-protein interactions, nucleotide binding states, and assembly chaperones or cofactors.

Formation proceeds through initial contact between hexamer units, followed by progressive oligomerization and, when necessary, conformational rearrangements. Assembly is often regulated by cellular conditions, such as nucleotide availability, ionic strength, or the presence of scaffold proteins, ensuring proper size and morphology.

Examples include the hexameric assemblies that form the core of some viral capsids, where many hexamers pack into a lattice with occasional pentamers to close the shell; HIV-1 is a well-studied instance where hexameric CA subunits assemble into a lattice that constitutes the mature capsid. In eukaryotic DNA replication, the MCM2-7 complex is a hexameric helicase essential for genome unwinding, illustrating a functional role for a native hexamer in higher-order assemblies.

Characterization of multihexamers relies on cryo-electron microscopy, X-ray crystallography, and mass spectrometry, which reveal subunit organization, symmetry, and stoichiometry.