Received: August 16, 2004, Accepted: November 3, 2004, Published online: July 1, 2005.

A NOVEL Kv1.1 POTASSIUM CHANNEL BLOCKING TOXIN FROM THE VENOM OFPalamneus gravimanus (INDIAN BLACK SCORPION)

MORE S. S. (1), MIRAJKAR K. K. (1), GADAG J. R. (1), MENON K. S. (2), MATHEW M. K. (2)

(1) Research Laboratory, Department of Biochemistry, Toxinology Division, Karnataka University, Dharwad, Karnataka, India; (2) National Centre for Biological Sciences, Tata Institute of Fundamental Research, UAS-GKVK, Bangalore, Karnataka, India.

ABSTRACT: A peptide toxin was isolated from the venom of Palamneus gravimanus, the Indian black scorpion, to block human Kv1.1 channels expressed in Xenopus laevis oocytes. A 4.5 kD peptide (toxin), as confirmed by SDS-PAGE, was purified to homogeneity by ion exchange chromatography using CM-Sephadex C-25 followed by Sephadex G-50 gel filtration. Palamneus gravimanus toxin (PGT) selectively blocks the human cloned voltage-gated potassium channel hKv1.1 in a two-electrode voltage-clamp (TEVC) technique. The results obtained indicate that the toxin blocks the hKv1.1 channel at a nanomolar concentration range (Ki value of 10 nM) of the peptide to the external side of the cell. The blockage seems to be voltage-dependent. Comparative structure of PGT (a 4.5 kD peptide) with BTK-2 suggests a close relationship; therefore this toxin can be employed to investigate the hKv1.1 channel structure.

KEY WORDS: hKv1.1, K+ channel, PGT, TEVC, Palamneus gravimanus, Xenopus laevis oocytes, Indian black scorpion.

CORRESPONDENCE TO: J. R. GADAG, Department of Biochemistry, Toxinology Division, Karnataka University, 580003, Dharwad, Karnataka, India.

Email: sunilacr@yahoo.co.in