The hierarchy has 12 levels, namely, from top to bottom: QS topology, QS family, QS, QS20, QS30…QS100. At the top of the hierarchy, there are 192 QS topologies. One particular QS topology (orange circle) with four subunits is expanded below. It comprises 161 *QS families* in total, of which two are detailed: the E. coli lyase and the H. sapiens hemoglobin γ_{4}. All complexes in the E. coli lyase QS family are encoded by a single gene and therefore correspond to a single QS. However, the hemoglobin QS Family contains two QSs: one with a single gene, the hemoglobin γ_{4}, and one with two genes, the hemoglobin α_{2}β_{2} from H. sapiens. The last level in the hierarchy indicates the number of structures found in the complete set (PDB). There are 30 redundant complexes corresponding to the lyase QS, four corresponding to the hemoglobin γ_{4} QS, and 80 to the hemoglobin α_{2}β_{2} QS. We also see that there are 9,978 monomers, 6,803 dimers, 814 triangular trimers, etc. Note that there are intermediate levels using sequence identity thresholds (fourth to twelfth level) between the QS level and the complete set, which are not shown in detail here.

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