- Protomer
In
structural biology , a protomer consists of one singleprotein subunit or several different subunits, that assemble in a definedstoichiometry to form anoligomer . The protomer is the smallest subset of different subunits that form the oligomer. The protomers usually arrange incyclic symmetry to form closedpoint group symmetries .Examples:
Different polypeptide chains (subunits) are conventionally designated by Greek letters. The number of each subunit in the oligomeric complex is indicated by the subscript number, similar to a chemical formula of elements.Hemoglobin consists of two α-chains and two β-chains. The oligomer stoichiometry is thus α2β2. Hemoglobin is a heterotetramer consisting of four subunits (two α and two β). It is a dimer of two αβ-protomers.Aspartate carbamoyltransferase has a α6β6 subunit composition. The six αβ-protomers are arranged in D3 symmetry.
Wikimedia Foundation. 2010.