R-Phycocyanin from red algae Porphyra spp: Binding of selected heavy metal ions

Abstract

Phycobiliproteins are major photosynthetic accessory pigments in cyanobacteria and red algae. Their vivid colours arise from covalently attached tetrapyrrole chromophores. The exciting characteristic of tetrapyrrole chromophores is the ability to bind metal ions. Heavy metals are among the most abundant and most dangerous environmental pollutants, and their removal from the environment is a crucial challenge. Therefore, utilizing PBPs-metal binding properties could be helpful in heavy metal detection and/or removal. The main aim of this study is to characterize the binding of selected heavy metal ions (Hg2+, Pb2+, Cd2+) to R-phycocyanin (R-PC) isolated and purified from red algae Porphyra spp.The protein fluorescence quenching approach revealed the strong binding affinity of R-PC to Hg2+ (Kd~0.1 μM), while protein binding to Pb2+ and Cd2+ is lower (Kd~3 μM) but still in the high to moderate range. Circular dichroism spectroscopy demonstrated the ability of Hg2+, Pb2+ and Cd2+ to slightly -helical content) in R-PC. Our results indicatethat R-PC could beexploited as a potential biosensor for heavy metal ions detection (especially Hg2+) in aquatic systems as well as in their removal from the environment (e.g. waste-water management).