homohexamer

A homohexamer is a protein complex composed of six identical polypeptide subunits, forming a single functional quaternary structure. In this arrangement, all subunits are the same sequence and fold, distinguishing it from heterohexamers that contain six different subunits.

The six subunits typically organize into one of a few common architectures. A ring-shaped assembly with sixfold symmetry (C6) is a frequent form, providing a central channel or pore in some cases. Another common arrangement is a trimer of dimers (D3 symmetry), where three dimers pair to create the hexamer. Interfaces between neighboring subunits create the catalytic sites or binding surfaces, enabling coordinated activity across the complex.

Formation of a homohexamer involves noncovalent interactions that promote subunit association. Oligomerization can be essential for function, as active sites may be formed at subunit interfaces or regulated by conformational changes transmitted around the ring. Allosteric communication between subunits often enables cooperative behavior and rapid responses to ligands or substrates. In some contexts, hexameric assemblies also contribute structural stability or form pore-like features that participate in transport or gating.

Homohexamers are found across domains of life and include enzymes, molecular machines, and regulatory complexes. Studying their structure and assembly informs understanding of catalytic mechanisms, regulation by oligomerization, and potential applications in protein design and nanotechnology. Structural characterization is typically achieved through X-ray crystallography and cryo-electron microscopy, complemented by biochemical assays and sequence-based analyses to identify conserved interface regions.