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:

Upadhyay, S.K., Nagarajan, P. and Mathew, M.K. (2009). Potassium channel opening: A subtle two step . Journal of  Physiology, 587, 3851–3868.

Usman, H., Kumari, S. and Mathew, M.K. (2010). Tumor suppressor candidate KCNRG   regulates surface expression of Shaker type potassium channels Biochem Biophys Res. Commun 391, 1301–1305.

Kumar GS, Upadhyay S, Mathew MK, Sarma SP (2011). Solution structure of BTK-2, a novel hK(v)1.1 inhibiting scorpion toxin, from the eastern Indian scorpion Mesobuthus tamulus. Biochim Biophys Acta. Apr;1814(4):459-69. Jan 21.

Shrivastava R, Basu B, Godbole A, Mathew MK, Apte SK, Phale PS (2011). Repression of the glucose-inducible outer-membrane protein OprB during utilization of aromatic compounds and organic acids in Pseudomonas putida CSV86. Microbiology.May;157(Pt 5):1531-40. Feb 17.

Krishnamurthy P, Ranathunge K, Nayak S, Schreiber L, Mathew MK.(2011) Root apoplastic barriers block Na+ transport to shoots in rice (Oryza sativa L.). J Exp Bot. Aug;62(12):4215-28. May 9.

Godbole A, Mitra R, Dubey AK, Reddy PS, Mathew MK.(2011) Bacterial expression, purification and characterization of a rice voltage-dependent, anion-selective channel isoform, OsVDAC4. J Membr Biol. Nov;244(2):67-80. Nov 6.