Fold: 4-helical cytokines

core: 4 helices; bundle, closed; left-handed twist; 2 crossover connections

Lineage:

1. Root: scop
2. Class: All alpha proteins
3. Fold: 4-helical cytokines
   core: 4 helices; bundle, closed; left-handed twist; 2 crossover connections

Superfamilies:

1. 4-helical cytokines (3)
   there are two different topoisomers of this fold with different entanglments of the two crossover connections
   1. Long-chain cytokines (10)
   2. Short-chain cytokines (9)
   3. Interferons/interleukin-10 (IL-10) (10)
      contains an additional helix in one of the crossover connections