Protein subunit

[5] For example, ATP synthase has a type of subunit called α.

Three of these are present in the ATP synthase molecule, leading to the designation α3.

[6] Naturally occurring proteins that have a relatively small number of subunits are referred to as oligomeric.

[9] The subunits of a protein complex may be identical, homologous or totally dissimilar and dedicated to disparate tasks.

[11] An enzyme composed of both regulatory and catalytic subunits when assembled is often referred to as a holoenzyme.

Rendering of HLA-A11 showing the α (A*1101 gene product) and β (Beta-2 microglobulin) subunits. This receptor has a bound peptide (in the binding pocket ) of heterologous origin that also contributes to function.