title: Crystals of a 1:1 complex between human interleukin-4 and the extracellular domain of its receptor alpha chain.
abstract: The specific high-affinity binding of interleukin-4 (IL-4) to its receptor alpha chain is the crucial primary event during IL-4 signalling. Single crystals, suitable for high resolution diffraction studies, have been obtained from a complex between IL-4 and the ectodomain of the receptor alpha chain, also called IL-4-binding protein (IL-4BP). The orthorhombic crystals are in spacegroup P2(1)2(1)2(1) with cell constants a = 5.038 nm, b = 6.841 nm, c = 10.95 nm and diffract to a resolution of at least 0.25 nm when exposed to synchrotron radiation. The volume of the unit cell suggests the presence of a 1:1 IL-4/IL-4BP complex and HPLC analysis of the crystals confirmed that IL-4 and IL-4BP were present in equimolar amounts. An IL-4 variant comprising a total of four methionine residues was generated, labelled with selenomethionine and crystallised in complex with IL-4BP. The crystals are isomorphous to that of the complex with normal IL-4 and therefore can be used to solve the crystallographic phase problem by the method of multiple anomalous diffraction (MAD). The crystal structure of the IL-4/IL-4BP complex will help to understand how IL-4 and other helical cytokines bind and activate their cognate receptor.
authors.affiliation: Theodor-Boveri-Institut für Biowissenschaften (Biozentrum), Physiologische Chemie II der Universität, Würzburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Hage
authors.forename: P
authors.initials: P
authors.lastname: Reinemer
authors.forename: W
authors.initials: W
authors.lastname: Sebald
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015847:Interleukin-4 / Q000737:chemistry*; D011485:Protein Binding / Q000502:physiology; D019948:Receptors, Interleukin-4 / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D012645:Selenomethionine / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D019948:Receptors, Interleukin-4; D011994:Recombinant Proteins; D015847:Interleukin-4; D012645:Selenomethionine