IDENTIFICATION OF FC-GAMMA-RIIA, A PRODUCT OF THE MURINE ALPHA-FC-GAMMA-R GENE

Two genes, α and β, encode murine low‐affinity receptors for the Fc portion of IgG (FcγRII). The amino acid sequences deduced from the nucleotidic sequences of α and β cDNA are highly homologous in extracellular domains. As a consequence, the protein product of the αFcγR gene has not yet been distinguished from that of the βFcγR gene, α and β cDNA, however, show no homology in sequences coding for intracellular portions. We therefore raised antibodies against a synthetic peptide corresponding to the 26 intracytoplasmic amino acids of the expected product of the murine αFcγR gene. F(ab')2 fragments of α‐specific antibodies thus obtained stained specifically membrane proteins which were present in cells containing α transcripts but not in cells containing β transcripts only; they bound molecules carrying the 2.4G2 epitope, characteristic of the extracellular domains of murine FcγRII; they immunoprecipitated material which migrated as heterogeneous glycosylated proteins of 45–55 kDa when native and, when deglycosylated, as a single polypeptide with an apparent molecular mass of 29 kDa, which is compatible with the calculated molecular mass of the protein expected to be translated from αFcγR transcripts. These criteria identify a product of the murine αFcγR gene as a subtype of FcγRII which can be designated FcγRIIa. Copyright © 1990 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim