Characterization of the murine homing receptor gene reveals correspondence between protein domains and coding exons.

Lymphocytes and other leukocytic cells traffic to diverse lymphoid organs and sites of inflammation by utilizing an adhesion molecule termed the homing receptor. Characterization of the cDNAs encoding the murine lymphocyte homing receptor has revealed an interesting mosaic structure containing three well-known protein motifs: a C-type lectin domain, an epidermal growth factor-like domain, and two exct copies of a short consensus repeat sequence homologous to those found in a family of complement regulatory proteins, in addition to a signal sequence, a transmembrane anchor, and a short cytoplasmic tail. Characterization of genomic clones encoding the murine homing receptor gene has revealed a high degree of correlation between these various structure/function motifs and exons that specify them. Interestingly, comparison of the exons encoding the two identical copies of the complement regulatory motif revealed that short intronic regions 5\u27 and 3\u27 of these exactly repeated exons are also identical. The gene was found to map to a region of chromosome 1, very near a site previously shown to contain the genes for the family of complement regulatory proteins which encode short consensus repeats similar to those found in the homing receptor, implying that these diverse proteins may have evolved in part by repeated duplications