Prokineticin-2 (PK2) is a cysteine-rich secreted protein that is expressed in the testis and in lower levels of the small intestine. PK2 regulates various biological functions including gastrointestinal motility, angiogenesis and circadiam rhythms. It is closely related to EG-VEGF (Prokineticin-1) and binds to two orphan B-protein-coupled receptors termed PK-R1 and PK-R2. Recombinant human Prokineticin-2 is an 8.8 kDa protein consisting of 81 amino acid residues and ten cysteine residues that potentially form five pairs of intra-molecular disulfide bonds.