Full length cDNA clones encoding the mouse FcγRI were isolated by using redundant oligonucleotide probes based on previously determined amino acid sequence of protein bound to an IgG2a antibody column. Sequence analysis of cDNA clones indicates that mouse FcγRI is a transmembrane glycoprotein that is composed of three disulfide bonded extracellular Ig binding domains unlike FcγRII of man and mouse. These extracellular domains contain five potential sites of N-linked glycosylation; three sites in the first domain and one in each of the second and third domains. In addition a transmembrane region is present followed by a cytoplasmic tail of 84 amino acids. Analysis of the amino acid sequence of the first two extracellular domains of FcγRI indicate that these are highly homologous to the extracellular domains of FcγRII; the third domain is different and shows a lower level of homology to other FcR domains but is clearly related to the Ig superfamily. Transfected cells expressing FcγRI were shown to bind immune complexes of rabbit IgG; and monomeric IgG2a bound to transiently transfected cells with an affinity of approximately 5 x 107 M-1, i.e. the receptor was of high affinity and therefore was by definition FcγRI. Northern analysis demonstrated that FcγRI mRNA could be detected in the FcγRI+ myeloid cell lines WEH1 3B and J774. Finally, Southern analysis indicated that FcγRI is likely to be encoded by a single copy gene of ~9 kb.
|Number of pages||8|
|Journal||Journal of Immunology|
|Publication status||Published - 1 Jan 1990|