A protein with a core domain architecture consisting of an extracellular domain containing two or three copies of the Immunoglobulin domain (Pfam:PF00047), followed by a single-pass transmembrane region and a small intracellular domain. The active protein is a low affinity receptor for immunoglobulin gamma chain Fc region. It comprises the translation products of the FCGR1 gene (mouse) or one of the closely related FCGR1A, FCGR1B, or FCGR1C genes (human). FCGR1C may be a pseudogene in human. [ ]