Identification and functional analysis of cadmium-binding protein in the visceral mass of Crassostrea gigas

Abstract

The Pacific oyster, Crassostrea gigas, is a traditional food worldwide. The soft body of the oyster can easily accumulate heavy metals such as cadmium (Cd). To clarify the molecular mechanism of Cd accumulation in the viscera of C. gigas, we identified Cd-binding proteins. 5,10,15,20-Tetraphenyl-21H,23H-porphinetetrasulfonic acid, disulfuric acid, tetrahydrate, and Cd-binding competition experiments using immobilized metal ion affinity chromatography revealed the binding of water-soluble high molecular weight proteins to Cd, including C. gigas protein disulfide isomerase (cgPDI). Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analyses revealed two CGHC motifs in cgPDI. The binding between Cd and rcgPDI was confirmed through a Cd-binding experiment using the TPPS method. Isothermal titration calorimetry (ITC) revealed the binding of two Cd ions to one molecule of rcgPDI. Circular dichroism (CD) spectrum and tryptophan fluorescence analyses demonstrated that the rcgPDI bound to Cd. The binding markedly changed the two-dimensional or three-dimensional structures. The activity of rcgPDI measured by a PDI Activity Assay Kit was more affected by the addition of Cd than by human PDI. Immunological analyses indicated that C. gigas contained cgPDI at a concentration of 1.0 nmol/g (viscera wet weight). The combination of ITC and quantification results revealed that Cd-binding to cgPDI accounted for 20% of the total bound Cd in the visceral mass. The findings provide new insights into the defense mechanisms of invertebrates against Cd.

The Spatial Distribution Patterns, Physicochemical Properties, and Structural Characterization of Proteins in Oysters (Crassostrea hongkongensis)

“…The digestion of SSP was inhibited by protein oxidation and aggregation [ 7 , 8 ]. The proteins from different parts of the oyster (visceral mass, mantle, gill, and adductor) had different abilities to bind metals such as Cd, Zn, and Cu, indicating that metal-binding ability correlates with the protein type [ 9 , 10 , 11 , 12 ]. Oyster proteins (e.g., WSP, SSP, ASP and ALSP) have different physicochemical, functional, and structural properties, and are suitable for different processing methods [ 7 , 8 , 13 , 14 , 15 , 16 , 17 ].…”

Deposition of Lead Phosphate by Lead-Tolerant Bacteria Isolated from Fresh Water near an Abandoned Mine

“…For example, heavy metals accumulate in seeds and cause physiological dysfunctions and malnutrition in plants [ 1 ]. Heavy metals accumulate in plants and animals and cause irreversible damage at the cellular level, where they inhibit enzyme activity, disturb the functioning of essential elements, and promote the prevalence of reactive oxygen species [ 2 , 3 , 4 ].…”