J. Biol. Chem., Vol. 261, Issue 21, 9801-9804, 07, 1986
Preparation of 32P-labeled murine immune interferon and its binding to the mouse immune interferon receptor
JA Langer, A Rashidbaigi and S Pestka
Murine immune interferon (Mu-IFN-gamma) can be radiolabeled with [gamma-
32P]ATP by the catalytic subunit of cAMP-dependent protein kinase. The
resulting 32P-labeled Mu-IFN-gamma (32P-Mu-IFN-gamma) with high
radiological specific activity (60-260 muCi/micrograms) retains biological
activity. Acid hydrolysis of 32P-Mu-IFN-gamma or 32P-labeled human
IFN-gamma leads to the release of [32P]phosphoserine but not
phosphothreonine or phosphotyrosine. With 32P-Mu-IFN-gamma, we have
demonstrated that there are 5 X 10(3) to 1.5 X 10(4) receptors per-cell on
several murine cell lines of diverse origin and that the Kd at 24 degrees C
for these cells is in the range of 1 X 10(-10) to 1 X 10(-9) M. Covalent
binding of 32P-Mu-IFN-gamma to its receptor results in the formation of
several specific high-molecular weight products, the major one of which has
an apparent molecular weight of 90,000-100,000. If this represents a 1:1
complex of Mu-IFN-gamma and its receptor (or its binding subunit), the
murine interferon gamma receptor has a molecular weight of 75,000-85,000.