Proton/potassium ATPase of Leishmania (in collaboration with Professor Antony Mukkada):

Leishmaniasis is a tropical disease caused by a protozoan parasite. Several forms of the disease are caused by different species of Leishmania. In particular, the organism (Leishmania donovani) transmitted by the bite of the sand flea, is very difficult to kill because it invades, grows and reproduces inside human macrophage cells. Current research has focussed on some of the factors influencing the intracellular survival of the parasite in the amastigote form; especially, those factors involved in the maintenance of the balance of nutrients and the survival of the parasites in the hostile environment of a macrophage. The phagocytic vesicle in the macrophage would typically kill and digest any foreign cells that are ingested by the macrophage. The vesicle normally is quite acidic (i.e., has a very low pH) and contains digestive enzymes that are active in that environment. In order for the amasitgote to survive and thrive in that environment, it must be able to counter the attack. It must not have exposed surface materials that are susceptible to the digestive enzymes. Also, it must be able to maintain an internal pH in the physiological range (around pH 7) while taking in nutrients and necessary ions against a gradient. By now, there is considerable evidence to show that pH balance is achieved through an exchange of protons for potassium ions catalyzed by an ion-pumping ATPase.

Research approach:

1. Characterization of the proton/potassium ATPase. This approach involves isolation of the intact ATPase from cell membranes, demonstrating activity, especially in reconstituted membrane systems, determining the apparent molecular weight, subunit components, sequence of amino acids, etc. Once isolated enzyme is available, further studies of the conformation, substrate and inhibitor binding sites, genomic sequence, etc. become possible.
2. A continuing study of various physiological processes of the parasite and the invaded host cells, trying to find ways to understand the biochemical bases of the physiological processes. An attempt will be made to correlate physiology with specific gene products.