Toxicological Significance of Silicon-protein Interaction

Abstract

In order to understand the molecular mechanism of the toxicity of Si containing particulate air pollutants, the interaction between silicate anion and proteins was studied. On the basis of molecular sieving profile, the presence of a protein fraction capable of binding silicic acid was detected in rat lung and serum. The binding is firm being able to withstand dialysis, Si-binding by Bovine Serum Albumin (BSA) follows stoichiometric principles indicating true chemical reaction in terms of effects of pH, temperature and period of incubation. Fluorescence spectrum of the BSA-Si complex decreased with an increase in Si concentration. Effect of Si-binding on trypsin activity against albumin showed that proteins other than albumin could also interact with Si-trypsin containing silica showed distinctly low, catalytic activity against native BSA. When both the substrate and enzyme contained bound Si, the activity further reduced by 36 per cent as compared to both pure trypsin and pure BSA, clearly indicating that binding of Si with substrate or enzyme proteins can adversely effect the biological activity. Complexing with proteins is likely to play a role in pathogenesis of pneumoconiosis, elimination of dusts, formation of silicate stones in plants and animals, and possibly in the reported role of Si in nutrition, cardiovascular diseases and ageing.