This domain is found in Interleukin-7 receptor subunit alpha (IL-7Ralpha), which together IL-7 form a complex crucial to several signalling cascades leading to the development and homeostasis of T and B cells. IL-7Ralpha carries a 219 residue ectodomain on the N-terminal region which is crucial for T and B-cell development. Mutations in the IL-7Ralpha ectodomain inhibits T and B cell development, resulting in patients with a form of severe combined immunodeficiency (SCID). The ectodomain folds into two fibronectin type III (FNIII) domains connected by a 310-helical linker. This entry comprises the first of the two FNIII domains, D1 while D2 domain is Pfam:PF00041. In the D1 domain of IL-7Ralpha, a disulfide bond (C22R-C37R) conserved among cytokine receptor class I (CRH I) family members bridges two beta strands [1].

1: Structural and biophysical studies of the human IL-7/IL-7Ralpha complex. McElroy CA, Dohm JA, Walsh ST; Structure. 2009;17:54-65. PMID:19141282

2: Structural reorganization of the interleukin-7 signaling complex. McElroy CA, Holland PJ, Zhao P, Lim JM, Wells L, Eisenstein E, Walsh ST; Proc Natl Acad Sci U S A. 2012;109:2503-2508. PMID:22308406

3: Structural basis of the proinflammatory signaling complex mediated by TSLP. Verstraete K, van Schie L, Vyncke L, Bloch Y, Tavernier J, Pauwels E, Peelman F, Savvides SN; Nat Struct Mol Biol. 2014;21:375-382. PMID:24632570