UBC Theses and Dissertations

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UBC Theses and Dissertations

Pseudo-nitzchia multiseries ferritin iron oxidation and oxidative stress protection in the presence of glutathione Woolcock, Jennifer


Iron is an essential nutrient for most organisms, including diatoms. A portion of intracellular iron is attributed to the labile iron pool (LIP), which is readily exchangeable iron available to bind to enzymes to participate in biological reactions. Iron belonging to the LIP is transiently bound to cellular ligands, such as glutathione (GSH). However, iron present in the cell in excess can be toxic to the cell, as ferrous iron can react with H₂O₂ in the Fenton reaction to produce highly detrimental reactive oxygen species (ROS). Pseudo-nitzchia multiseries is a marine planktonic diatom that plays an important role in primary production and carbon sequestration in the ocean. P. multiseries expresses an iron storage protein, ferritin (PmFtn), which protects the cell from oxidative damage by oxidizing iron at ferroxidase centres and storing iron in a nano-cage formed from 24 monomers. Ferritin ferroxidase activity is poorly characterized in the presence of biologically-relevant iron chelators of the LIP. In this study, PmFtn ferroxidase activity was found to proceed at a slower rate in the presence of GSH. In a PmFtn structure obtained from a crystal soaked in the presence of iron and GSH for 30 minutes, iron was found bound to the ferroxidase centre at sites A and B, consistent with spectroscopic data showing rapid binding of iron but slow mineralization in the presence of GSH. PmFtn and GSH also protected DNA from H₂O₂ mediated oxidative stress in the presence of iron.

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