The EGF module-containing Mucin-like hormone Receptors (EMRs) are closely related subgroup of G protein-coupled receptor

G protein-coupled receptor

G protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors , comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal...

s (GPCRs). These receptors have a unique hybrid structure in which an extracellular epidermal growth factor

Epidermal growth factor

Epidermal growth factor or EGF is a growth factor that plays an important role in the regulation of cell growth, proliferation, and differentiation by binding to its receptor EGFR...

 (EGF)-like domain is fused to a GPCR domain through a mucin

Mucin

Mucins are a family of high molecular weight, heavily glycosylated proteins produced by epithelial tissues in most metazoans. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell...

-like stalk. There are four variants of EMR labeled 1-4, each encoded by a separate gene. These receptors are predominately expressed in cells of the immune system and bind ligands such as CD55.