Organization of the gene encoding the human macrophage mannose receptor (MRC1).
The gene for the human macrophage mannose receptor (MRC1) has been characterized by isolation of clones covering the entire coding region. Sequence analysis reveals that the gene is divided into 30 exons. The first three exons encode the signal sequence, the NH2-terminal cysteine-rich domain, and the fibronectin type II repeat, while the final exon encodes the transmembrane anchor and the cytoplasmic tail. The intervening 26 exons encode the eight carbohydrate-recognition domains and intervening spacer elements. However, no simple correlation between intron boundaries and functional carbohydrate-recognition domains is apparent. The pattern of intron positions as well as comparison of the sequences of the carbohydrate-recognition domains suggests that the duplication of these domains was an evolutionarily ancient event.