multiprotein

Multiprotein refers to biological assemblies composed of multiple protein subunits that come together to form a functional unit. Such complexes can be heteromeric, containing different subunits, or homo-oligomeric, formed from identical subunits. Subunits interact through non-covalent contacts and sometimes bind non-protein cofactors. Assembly can be stable over the cell’s life or dynamic, with subunits exchanging in response to cellular conditions.

Multiprotein complexes perform a wide range of cellular tasks, including catalysis, structural support, signaling, gene expression, and processing of macromolecules. Notable examples include the ribosome, the proteasome, RNA polymerase II transcription machinery, the spliceosome, and various chromatin-remodeling or DNA-replication complexes. Many complexes act as platforms that bring enzymes, adaptors, and substrates into proximity, facilitating coordinated activity.

Architectures are often modular, with a core catalytic or structural module surrounded by regulatory subunits. Assembly is guided by scaffolding proteins and chaperones and regulated by post-translational modifications, localization, and partner availability. In cells, assembly and disassembly can occur in dedicated compartments or during processes such as transcription, replication, or vesicular trafficking. Dynamic remodeling enables rapid responses to signals and changing conditions.

Studying multiprotein complexes uses techniques such as co-immunoprecipitation, affinity purification coupled with mass spectrometry, cryo-electron microscopy, cross-linking, and other structural methods. Defects in subunit expression or assembly are linked to diseases including cancers and neurodegenerative disorders, underscoring the importance of understanding multiprotein organization and regulation.