Figure 1

Human Class I receptor chains and complexes. a) Topological representation of the five structural groups of Class I receptor chains adapted from Boulay et al, 2003 [10]. Depicted are the Immunoglobulin-like (Ig) domains, Cytokine receptor Homology Domains (CHDs), including conserved cysteines (thin bands) and WSXWS motifs (thick band), Fibronectin type III (FBN) domains, Transmembrane (TM) regions, and Intracellular Homology Region (IHR) sequences. Full receptor names can be found in the list of abbreviations. b) Assembly of Class I receptor chains into functional receptor complexes. Individual receptor chains form either homodimers or various heterocomplexes that bind to specific ligands. For receptor complexes that bind to multiple cytokines, only one receptor complex is listed. Although constituents of receptor complexes of the IL-2R functional family, the IL-2Rα and IL-15Rα receptor chains are not members of the Class I family of receptors, but instead contain distinctive 'sushi domain' structures [55]. The orphan receptor chain CLF-3 was not included as its arrangement into a receptor complex is yet to be established.