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Interaction of Chloroquine and Its Analogues with Heme: An Isothermal Titration Calorimetric Study

Bachhawat, Kiran and Thomas, Celestine J and Surolia, Namita and Surolia, Avadhesha (2000) Interaction of Chloroquine and Its Analogues with Heme: An Isothermal Titration Calorimetric Study. In: Biochemical and Biophysical Research Communications, 276 (3). pp. 1075-1079.

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Quinoline-containing drugs such as chloroquine and quinine have had a long and successful history in antimalarial chemotherapy. Identification of ferriprotoporphyrin IX ([Fe(III)PPIX], haematin) as the drug receptors for these antimalarials called for investigations of the binding affinity, mode of interaction, and the conditions affecting the interaction. The parameters obtained are significant in recent times with the emergence of chloroquine resistant strains of the malaria parasites. This has underlined the need to unravel the molecular mechanism of their action so as to meet the requirement of an alternative to the existing antimalarial drugs. The isothermal titration calorimetric studies on the interaction of chloroquine with haematin lead us to propose an altered mode of binding. The initial recognition is ionic in nature mediated by the propionyl group of haematin with the quaternary nitrogen on CQ. This ionic interaction induces a conformational change, such as to favour binding of subsequent CQ molecules. On the contrary, conditions emulating the cytosolic environment (pH 7.4 and 150 mM salt) reveal the hydrophobic force to be the sole contributor driving the interaction. Interaction of a carefully selected panel of quinoline antimalarial drugs with monomeric ferriprotoporphyrin IX has also been investigated at pH 5.6 mimicking the acidic environment prevalent in the food vacuoles of parasite, the center of drug activity, which are consistent with their antimalarial activity.

Item Type: Journal Article
Publication: Biochemical and Biophysical Research Communications
Publisher: Academic Press
Additional Information: Copyright of this article belongs to Academic Press.
Keywords: Chloroquine;Heme;Isothermal titration calorimetry
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 09 Oct 2007
Last Modified: 19 Sep 2010 04:40
URI: http://eprints.iisc.ac.in/id/eprint/12161

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