Depuration mechanism of Cd2+ from blue mussel based on molecular simulation analysis

Abstract: Proteolytic peptides-metal complexes is an organic trace element complexes which is made up of metal ions in soluble metal salt combined with peptides by covalent bonds with certain mole ratio, which has characteristics of quick absorption, good palatability, high biological titer, etc. Previous studies have showed that protein peptide hydrolysis-metal complexes in the blue mussel (Mytilus edulis) and Procambarus clarkia have good effect on Cd2+ detoxification and removal. The purpose of this study was to investigate the depuration mechanism of cadmium ion (Cd2+) from blue mussel (Mytilus edulis) based on homology modeling, dynamic simulation, and interaction energy analysis. The prepared hydrolysis peptides-Fe2+ complexes (TPH-Fe2+) were added in cultured seawater to remove Cd2+. The results indicated that the significant differences (P<0.05) were observed in the group by feeding 40 mg/L TPH-Fe2+. The initial Cd2+ concentration in mussel was 47.099 μg/g, then decreased to 24.221 μg/g after 15 day's feeding. Subsequently, the three-dimensional structure of β-domain in metallothionein (MT) from blue mussel was modeled by computer homology modeling technique, based on the MT template (1DFT) from the mouse. The results of molecular dynamics simulation and semiempirical quantum mechanic calculations indicated the depuration mechanisms as follows: the hydrolytic peptides (carriers) and chelated Fe2+ exhibited their activities in target organ cells after the absorption. It was hypothesized that the absorbed active peptides reduced the combined power between MT and Cd, resulting in the improvement of the turnover rate of MT. The released Fe2+ also showed a positive effect on the removal of Cd in blue mussel. For these reasons, TPH-Fe2+ is recommended as depuration agents in mussel feed to decrease the Cd concentrations in tissues.