Exploring the architecture and function of transmembrane ion transporters

The biological membrane is essentially impermeable to polar and charged solutes. This allows the cell to make separate compartments to carry out different functions. However, it also means that cells need specific proteins to transport these solutes across membranes. We study a variety of transporters in systems ranging from plants to nerve cells in an attempt to understand what these proteins look like and how their structures facilitate the functions they perform..

Electrical signalling in nerves is brought about by the movement of ions across the cell membrane. We use a combination of molecular biology and electrophysiology to investigate the mechanism by which the voltage-gated K⁺-channel opens and closes in response to changes in transmembrane potential.

Plants have evolved several mechanisms to survive salinity in the soil. In order to study the cellular basis of this tolerance we have generated suspension cell cultures from different rice cultivars. We have shown that surviving saline stress requires that cells maintain low Na⁺ concentrations in the cytosol. This is achieved both by reducing the permeability of the cell membrane to Na⁺ and by the activity of transporters present in the vacuole.

We have expressed an endoplasmic reticulum located Ca⁺⁺ pump of plant origin in yeast. Expression of this pump enables the yeast to survive high salinity in the medium by turning on a rarely used Na⁺ transporter in the vacuole.

Selected Publications:

1.       Anil VS, Krishnamurthy P, Kuruvilla S, Sucharitha K, Thomas G &  Mathew MK (2005) Regulation of the uptake and distribution of Na⁺ in shoots of rice (Oryza sativa L.) variety Pokkali: Role of Ca²⁺ in salt tolerance response  Physiol. Plantarum  124, 451 - 464

2.       Kavitha S, Varshney A & Mathew MK (2005) N type rapid inactivation in human Kv1.4 channels: Functional role of a putative  C- terminal helix Molec. Membr. Biol.  22, 389 – 400

3.          Anil A, Krishnamurthy H & Mathew MK (2007) Limiting Cytosolic Na⁺ Confers Salt Tolerance to Rice Cells in Culture: A Two-Photon Microscopy Study of  SBFI Loaded Cells  Physiol Plantarum 129, 607 – 621