CIONIN

Description

Cionin is the ascidian ortholog of vertebrate cholecystokinin.In 1990, cionin was isolated from the neural complex of an ascidian, Ciona intestinalis.

Structure

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.

Properties

Mol. wt. 1254.1370. Soluble in water, physiological saline solution, aqueous acetonitrile, and methanol.

Biological functions

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.

Synthesis and release

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.