This family consists of several prokineticin proteins and related BM8 sequences. The suprachiasmatic nucleus (SCN) controls the circadian rhythm of physiological and behavioural processes in mammals. It has been shown that prokineticin 2 (PK2), a cysteine-rich secreted protein, functions as an output molecule from the SCN circadian clock. PK2 messenger RNA is rhythmically expressed in the SCN, and the phase of PK2 rhythm is responsive to light entrainment. Molecular and genetic studies have revealed that PK2 is a gene that is controlled by a circadian clock [1].

1: Prokineticin 2 transmits the behavioural circadian rhythm of the suprachiasmatic nucleus. Cheng MY, Bullock CM, Li C, Lee AG, Bermak JC, Belluzzi J, Weaver DR, Leslie FM, Zhou QY; Nature 2002;417:405-410. PMID:12024206

2: Bv8, a small protein from frog skin and its homologue from snake venom induce hyperalgesia in rats. Mollay C, Wechselberger C, Mignogna G, Negri L, Melchiorri P, Barra D, Kreil G; Eur J Pharmacol 1999;374:189-196. PMID:10422759

3: The mammalian homologues of frog Bv8 are mainly expressed in spermatocytes. Wechselberger C, Puglisi R, Engel E, Lepperdinger G, Boitani C, Kreil G; FEBS Lett 1999;462:177-181. PMID:10580115