Intermolecular cystine-bonding of murine interleukin 2 indicates that ligand dimerization is important for the formation of the high-affinity receptor complex.
Interleukin 2 is thought to be active as a monomeric protein. As the nonessential Cys-140 of murine interleukin 2 (mIL2) is located in the hydrophobic interface of the amphiphilic F domain it was successfully used to stabilize hydrophobic amino acid contacts between two mIL2 cores yielding biologically active cystine-bonded dimeric mIL2. (3H) thymidine incorporation assays with intermolecular cystine-bonded or monomeric mIL2 revealed almost identical median effective concentrations (EC50) and high-affinity dissociation constants (Kdh), respectively. Comparative binding and internalization assays suggest that one cystine-bonded dimeric or two monomeric mIL2 molecules bind to the high-affinity receptor complex. Furthermore, DSS concentration-dependent crosslinking studies using monomeric mIL2 revealed four membrane-derived protein-complexes with apparent molecular weights of about 70 kDa, 85 kDa, 95 kDa and 100 kDa, respectively, showing that both mIL2 receptor chains may be crosslinked to a monomeric or dimeric ligand molecule, respectively. We therefore propose that dimerization of murine interleukin 2 occurring either in solution at concentrations above the low-affinity dissociation constant or at the low-affinity receptor is important for regulation of high-affinity complex formation and signal transduction.
Lother
H
H
Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Universität Hamburg, Federal Republic of Germany.
Müther
H
H
Gessner
A
A
Abdallah
S
S
Kühlcke
K
K
D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003553:Cystine / Q000378:metabolism*; D007376:Interleukin-2 / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D013388:Succinimides / Q000494:pharmacology
D003432:Cross-Linking Reagents; D007376:Interleukin-2; D008024:Ligands; D015375:Receptors, Interleukin-2; D013388:Succinimides; D003553:Cystine; C019358:disuccinimidyl suberate