Interaction Of Brain Cystatin With Dopamine: A Neurotransmitter

The term Cystatin (Thiol Proteinaseinhibitor) refers to proteins that specifically inhibit the activity of papain like lysosomal cysteine proteinases. They serve a protective function and regulate the activities of endogenous proteinases, which if not regulated may cause uncontrolled proteolysis and damage to cells and tissues. They are non covalent tight binding proteins which are widely distributed in animals, plants and microorganisms. Dopamine abbreviated as "DA” is an amino acid neurotransmitter; it is a chemical substance which is able to transmit a nerve message across a synapse. It is obtained through the normal diet and also synthesized in the brain. The enzyme monoamine Oxidase helps in maintaining the level of dopamine, an increase or decrease in dopamine level leads to schizophrenia and Parkinson’s disease respectively. Cystatin interacts with dopamine decreasing the level of dopamine in the brain and this might be a factor in Parkinson’s disease. In the present study when (1µM) of cystatin was treated with increasing concentration of dopamine , it showed decrease in fluorescence intensity with 20 nM of blue shift which is indicative of binding and changes in native structure of protein upon complexation. Binding investigation in this work, gives significant information about the conformational changes in cystatin due to interaction with dopamine; such studies may be used as a tool for drug designing and it might shed some light on the mechanism of action of dopamine as well as its side effect.