cDNA cloning and tissue distribution of calmodulin from sea cucumber (Stichopus monotuberculatus)

Calmodulin, a calcium ion binding protein, plays an important role in calcium signal transduction system. This study cloned the cDNA of calmodulin from Stichopus monotuberculatus (named as StmCaM) by using homology cloning method and RACE approach. StmCaM cDNA comprised 1 394 nucleotides, which contained a 138-bp 5UTR, an 806-bp 3UTR and a 450-bp ORF. StmCaM deduced from this ORF contained 149 amino acids including the initial Met，whose estimated molecular mass was 16.7 kDa and theoretical isoelectric point was 4.1. The amino acid sequences of StmCaM showed high similarity with other species CaMs, ranging from 95.9% to 98.0%. By utilizing real-time RCR to detect the expression pattern of CaM from different tissues of S.monotuberculatus, we found that respiratory tree had the highest mRNA expression level, followed by coelomocyte and intestine. However, body wall had the lowest expression level, which could hardly be detected.