Quaternary Subunit Structures of Proteins

Cyclic (Rotation) symmetry It is the simplest arrangement possible, involving isologous association of subunits. The disposition of the subunits is such that there is an n-fold rotational axis where n is the number of subunits. A rotation of 360°/n transposes the structure into itself. This type of symmetry is designated as Cn. 

Alcohol dehydrogenase is a dimeric protein with C2, and pyruvate carboxylase is a tetrameric protein with C4 symmetries respectively. The cyclic symmetry allows the polar 

Code No. Architecture Level name (Description) Example 

40 Alpha solenoid Peridinine chlorophyll protein, chtiin M 

50 Alpha/alpha barrel Glycosyl hydrolase, domain 2 

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