szubunit

Szubunit, in biology, is the Hungarian term for a single polypeptide chain or RNA molecule that is a component of a larger macromolecular complex. In biochemistry, many functional proteins exist as multimeric assemblies composed of multiple subunits. Subunits may be identical (homomeric) or different (heteromeric). They come together to form a holoenzyme, ribonucleoprotein, channel, or other molecular machine, and they often contribute distinct catalytic, binding, or structural roles. Subunit interactions are typically non-covalent, allowing reversible assembly and regulation.

Examples include the ribosome, which consists of small and large subunits; in bacteria, 30S and 50S combine to form the 70S ribosome, while in eukaryotes, 40S and 60S form the 80S ribosome. Hemoglobin is a tetramer composed of two alpha and two beta subunits, providing cooperative oxygen binding. Ion channels, receptors, proteasomes, and photosynthetic complexes also rely on multiple subunits that assemble to produce functional units.

Genetics and disease: Subunits are encoded by separate genes; expression, post-translational modification, and assembly control activity. Mutations or misassembly of subunits can impair function and cause diseases or influence drug responses. Terminology: In English texts, the word is 'subunit'; szubunit is the Hungarian form. See also quaternary structure, protein complex, oligomer, holoenzyme.