Modification of Lipid-Protein Organisation of Thylakoid Membrane by Means of Cadmium Ion

Abstract

An elevated level of cadmium in the environment is known to interact with different parts of the living system there by causing serious environmental hazards. When isolated chloroplasts are incubated in presence of cadmium ion in an isotonic buffer medium, the metal ion (Cd²⁺)found to induce thylakoid membrane lipid peroxidation and damage of electron transport system. It retards the loss of pigments and degradation of proteins. The cation induced membrane lipid peroxidation causes a drastic modification of lipid-protein organization of chloroplasts as reflected from changes in absorption and emission characteristics of the organelle.  The structural disorganization was attributed to the binding of metal ion to the thylakoid membrane surface through various functional groups viz. -SH, -COOH, -COOR, -OH etc. of proteins and lipids.  Such a binding exposed the lipid-protein organization for an easier entry and attack of reactive oxygen species, mainly singlet oxygen. The retardation of pigment and protein loss was due to cation induced stacking of thylakoid membrane.