This is the N-terminal Ig-like domain found in interleukin-13 receptor subunit alpha-1 (IL13RA1). IL13RA1 contains an extra N-terminal Ig-like domain not found in other receptors of the the common gamma-chain subfamily. The extra N-terminal Ig-like domain contacts the dorsal surfaces of both IL-4 and IL-13. The deletion of this domain has been shown to affect the binding of IL-13 to IL-13Ralpha1 [].
A number of receptors for lymphokines, hematopoietic growth factors and growth hormone-related molecules have been found to share a common binding domain. These receptors are designated as hematopoietin receptors []and the corresponding ligands as hematopoietins. Further, hematopoietins have been subdivided into two major structural groups: large (long) and small (short) hematopoietins.One subset of individual receptor chains that are part of receptor complexes for small hematopoietins contain common structural elements: an extracellular receptor domain that contains an immunoglobulin-like region at the N-terminal end; a transmembrane domain; and a short cytoplasmic domain. They define a structural subgroup containing the following chains:Granulocyte/macrophage colony stimulating factor receptor alpha (GMCSFRA)Interleukin-3 receptor alpha chain (IL3RA)Interleukin-5 receptor alpha chain (IL5RA)Interleukin-13 receptor alpha-1 chain (IL13RA1)Interleukin-13 receptor alpha-2 chain (IL13RA2)GMCSFRA, IL3RA or IL5RA chains of this subgroup bind to their cognate cytokines: GM-CSF, IL-3 and IL-5, with a common beta chain, KH97/AIC2B []. Either IL13RA1 chain or IL13RA2 chain form the IL13R complex together with IL4RA chain. IL-4 can compete with IL-13 to bind to either IL13R form [].
A number of receptors for lymphokines, hematopoietic growth factors andgrowth hormone-related molecules have been found to share a common bindingdomain. These receptors are designated as hematopoietin receptors []andthe corresponding ligands as hematopoietins. Further, hematopoietins have beensubdivided into two major structural groups: Large/long and small/shorthematopoietins.One subset of individual receptor chains that are part of receptor complexes for small hematopoietins are structurally related such that their extracellular parts strictly contain the 200 amino-acids hematopoietin domain (duplicated in IL-3/-5/GM-CSF beta chain receptors KH97/AIC2B and AIC2A). They define a structural subgroup containing the following chains: Interleukin-2 receptor beta chain (IL2RB), Interleukin-2 receptor common gamma chain (IL2RG), Interleukin-3 receptor beta chain (AIC2A), Interleukin-3/-5/GM-CSF receptor common beta chain (KH97/AIC2B), Interleukin-4 receptor alpha chain (IL4RA), Interleukin-7 receptor alpha chain (IL7RA), Interleukin-9 receptor alpha chain (IL9RA). A schematic representation of the structure of these receptors is shown below: +----------------------------------------xxxxxxx---------------------------+| C C C C Extracellular XXXXXXX Cytoplasmic |+-|-|-------|--|-------------------------xxxxxxx---------------------------+| | | | Transmembrane+-+ +--+IL4RA, IL7RA and IL9RA are specific alpha chain receptors for IL-4, IL-7and IL-9 respectively, whereas IL2RB is common to IL-2 and IL-15 (IL2RA andIL15RA are not members of the hematopoietin receptor superfamily). IL2RG ispart of IL-2, IL-15, IL-7, IL-9 and IL-4 form I receptor complexes [].KH97/AIC2B chain is part of GM-CSF, IL-3 and IL-5 receptor complexes and inthe mouse, AIC2B can be substituted by AIC2A, an IL-3 specific beta chainreceptor []. Together with either IL13RA1 or IL13RA2, IL4RA is also partof the IL-13 receptor complex for which IL-4 can compete with IL-13 (IL-4receptor complex form II) [].
