One of the primary objectives of our laboratory is to understand the molecular and physiological basis of survival of microbes in extreme conditions. For this, we have chosen three microbes namely.

Understanding the mechanism and biological significance of phospholipid translocation (flip-flop movement) of phospholipids across biological membranes

Phospholipids (PL) are the building blocks of cellular membranes. They possess the unique feature of having a hydrophobic tail and hydrophilic head group that helps them to arrange themselves in the form of an ultra thin and elastic bilayer, thus forming the membrane. However, these molecules face the problem of translocation across the biomembranes due to the energy barrier they have to overcome during the movement of their hydrophilic head group across the hydrophobic core of the biomembranes. The transbilayer movement of phospholipids across the model membranes in vitro is very slow (half time of translocation ~ hours to days). Nevertheless, lipid translocation across the cellular membranes is crucial during some physiological processes such as membrane fusion, exocytosis, endocytosis, apotosis, blood coagulation, activation of cells due to an immunoresponse and synthesis of new membranes. The phospholipid translocators in the biological membranes fall into four major classes, (i) Aminophospholipid translocase (APT), (ii) Multidrug resistance transporters (MDR), (iii) Phospholipid scramblases and (iv) Biogenic membrane flippases. The first two groups are present in the plasma membrane and translocates phospholipids in an ATP dependent manner, thus maintain the asymmetric distribution of plasma membrane (PM) PL. The third type is present in the PM and brings about a bidirectional and non-specific translocation of plasma membrane phospholipids when activated by a 103 fold increase in cytosolic Ca2+. The last group of proteins is present in the biogenic membranes (The membranes that synthesize other membranes in the cell e.g. the endoplasmic reticulum of eukaryotic cells and inner cell membranes of prokaryotic cells). Our laboratory focuses mainly on the scramblases and biogenic membrane flippases.