Prokineticins are secreted proteins that can promote angiogenesis and induce strong gastrointestinal smooth muscle contraction. The protein encoded by this gene is an integral membrane protein and G protein-coupled receptor for prokineticins. PKR2 is composed of 384 amino acids. Asparagine residues at position 7 and 27 undergo N-linked glycosylation.[5] Cysteine residues at position 128 and 208 form a disulfide bond.[5] The encoded protein is similar in sequence to GPR73, another G protein-coupled receptor for prokineticins.[6] PKR2 is also linked to mammalian circadian rhythm.[7] Levels of PKR2 mRNA fluctuate in the suprachiasmatic nucleus, increasing during the day and decreasing at night.[7]
Mutations in the PROKR2 (also known as KAL3) gene have been implicated in hypogonadotropic hypogonadism and gynecomastia.[8] Total loss of PKR2 in mice leads to spontaneous torpor usually beginning at dusk and lasting for 8 hours on average.[9]
PKR2 functions as a G protein-coupled receptor, thus it has a signaling cascade when it's ligand binds. PKR2 is a Gq-coupled protein, so when the ligand binds, beta-type phospholipase C is activated which creates inositol triphosphate. This then triggers calcium release inside the cell.[10]
