Cu2+ Inhibits the Peroxidase and Antibacterial Activity of Homodimer Hemoglobin From Blood Clam Tegillarca granosa by Destroying Its Heme Pocket Structure

Abstract

Beyond its role as an oxygen transport protein, the homodimer hemoglobin of blood clam Tegillarca granosa (Tg-HbI) has been found to possess antibacterial activity. However, the mechanism of antibacterial activity of Tg-HbI remain to be investigated. In this study, we investigated the effects of Cu2+ on the structure, peroxidase activity, and antibacterial ability of Tg-HbI. Tg-HbI was significantly inactivated by Cu2+ in a non-competitive inhibition manner, following first-order reaction kinetics. The Spectroscopy results showed that Cu2+ changed the iron porphyrin ring and the coordination of heme with proximal histidine of Tg-HbI, and increased the hydrophobicity of heme pocket. We found that proline could stabilize the heme pocket structure of Tg-HbI, hence, protect peroxidase activity and antimicrobial activity of Tg-HbI against damage by Cu2+. Our results suggest that Cu2+ inhibits the peroxidase and antibacterial activity of Tg-HbI by destroying its heme pocket structure and Tg-HbI probably plays an antibacterial role through its peroxidase activity. This result could provide insights into the antibacterial mechanism of Tg-HbI.

Structural Insights Into the Effects of Interactions With Iron and Copper Ions on Ferritin From the Blood Clam Tegillarca granosa

“…Moreover, De Meulenaere et al (2017) demonstrated that the conserved Glu131 residue at the 3-fold channel had been identified as a critical metal binding site in the Zn-bound structure of ChF. Wang et al also revealed that Hg 2+ ion could coordinate directly with the residues nearby its 3-fold channel of MjFer, largely impeding the entrance of ferrous ions ( Wang et al, 2021 ). Besides, several reports have suggested that the metal ions can conventionally bind to the highly conserved Asp and Glu residues within the 3-fold channel from the marine invertebrates S. constricta ferritin (ScFer) ( Su et al, 2020 ), Phascolosoma esculenta ferritin (PeFer and Fer147) ( Ming et al, 2021 ) and Dendrorhynchus zhejiangensis ferritin (DzFer) ( Huan et al, 2020 ).…”

“…The blood clam, Tegillarca granosa , is a marine invertebrate with important economic value that is broadly distributed in the sandy muds of the intertidal zone along the east coast of China and Southeast Asia. The bivalve shellfish T. granosa belongs to the family Arcidae, in the class Bivalvia (phylum Mollusca), and represents one of the rare invertebrates that possess hemoglobin-containing red hemocytes in the hemolymph ( Wang et al, 2021 ). Both ferritin and Cu 2+ ions can play crucial roles in the innate immune defense and antibacterial activity of T. granosa ( Jin et al, 2011 ; Wang et al, 2016 ; Wang et al, 2021 ); however, the interactions between T. granosa ferritin (TgFer) and both iron and copper ions remain unclear.…”

“…The bivalve shellfish T. granosa belongs to the family Arcidae, in the class Bivalvia (phylum Mollusca), and represents one of the rare invertebrates that possess hemoglobin-containing red hemocytes in the hemolymph ( Wang et al, 2021 ). Both ferritin and Cu 2+ ions can play crucial roles in the innate immune defense and antibacterial activity of T. granosa ( Jin et al, 2011 ; Wang et al, 2016 ; Wang et al, 2021 ); however, the interactions between T. granosa ferritin (TgFer) and both iron and copper ions remain unclear. In the present study, we present the first crystal structure for recombinant TgFer.…”

Genome-Wide Identification and Characteristic Analysis of Ets Gene Family in Blood Clam Tegillarca Granosa

“…It is widely distributed across the coastal regions of the Indo-Paci c area. T. granosa stands out among invertebrate taxa as possessing red hemocytes within its hemolymph that are enriched with hemoglobin [22]. The blood color of T. granosa is attributed to the abundance of hemoglobin in its hemocytes, resulting in a vibrant red hue [23,24].…”