Ligand binding induces a conformational change in ifnar1 that is propagated to its membrane-proximal domain.
The type I interferon (IFN) receptor plays a key role in innate immunity against viral and bacterial infections. Here, we show by intramolecular Förster resonance energy transfer spectroscopy that ligand binding induces substantial conformational changes in the ectodomain of ifnar1 (ifnar1-EC). Binding of IFN alpha 2 and IFN beta induce very similar conformations of ifnar1, which were confirmed by single-particle electron microscopy analysis of the ternary complexes formed by IFN alpha 2 or IFN beta with the two receptor subunits ifnar1-EC and ifnar2-EC. Photo-induced electron-transfer-based fluorescence quenching and single-molecule fluorescence lifetime measurements revealed that the ligand-induced conformational change in the membrane-distal domains of ifnar1-EC is propagated to its membrane-proximal domain, which is not involved in ligand recognition but is essential for signal activation. Temperature-dependent ligand binding studies as well as stopped-flow fluorescence experiments corroborated a multistep conformational change in ifnar1 upon ligand binding. Our results thus suggest that the relatively intricate architecture of the type I IFN receptor complex is designed to propagate the ligand binding event to and possibly even across the membrane by conformational changes.
Strunk
Jennifer Julia
JJ
Institute of Biochemistry, Johann Wolfgang Goethe-University, Biocenter N210, Max-von-Laue-Strasse 9, 60438 Frankfurt am Main, Germany.
Gregor
Ingo
I
Becker
Yvonne
Y
Li
Zongli
Z
Gavutis
Martynas
M
Jaks
Eva
E
Lamken
Peter
P
Walz
Thomas
T
Enderlein
Jörg
J
Piehler
Jacob
J
D031541:Fluorescence Resonance Energy Transfer; D016898:Interferon-alpha / Q000737:chemistry* / Q000378:metabolism; D016899:Interferon-beta / Q000737:chemistry* / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D053633:Receptor, Interferon alpha-beta / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature
D016898:Interferon-alpha; D021122:Protein Subunits; D053633:Receptor, Interferon alpha-beta; D016899:Interferon-beta