Cionin is the ascidian ortholog of vertebrate cholecystokinin.In 1990, cionin was isolated from the neural complex of
an ascidian, Ciona intestinalis.
Cionin is composed of 8 aa and conserves the C-terminal
amidated tetrapeptide (Trp-Met-Asp-Phe-NH2) of vertebrate
cholecystokinin (CCK)/gastrin. Two sulfated
tyrosines are present at positions 2 and 3.
Mol. wt. 1254.1370. Soluble in water, physiological
saline solution, aqueous acetonitrile, and methanol.
cior1 and cior2 are expressedmainly in the neural complex,
digestive organs, ovary, oral siphon, and atrial
siphon sperm of C. intestinalis.cior1 is highly expressed
in the stomach and middle intestine, whereas the expression
of cior2 is low in these tissues. In contrast, the expression
of cior2 is higher than that of cior1.3 No biological role
for cionin in C. intestinalis has been elucidated. Nevertheless,
cionin exhibited some CCK- or gastrin-like activity
in the vertebrate organ; the contraction of rainbow trout
gallbladders,and the release of histamine and gastric
acid in the rat stomach.
Gene, mRNA, and precursor:Cionin is encoded as a single copy in its precursor
peptide.Tissue distribution of mRNA:Cionin mRNA is expressed in numerous neurons in
the central nervous system and intestine of
C. intestinalis.
