The MVP channel is one of three putative potassium channels of the methanogenic deep-sea archaeon Methanococcus janaschii. For structural analysis the channel protein was expressed as a GST fusion protein in inclusion bodies of e-coli. After purification the protein was refolded using the detergent-based refolding technology designated M-FOLD^TM . This resulted in highly pure, monodispers and stable tetramers, that were used successfully for crystallistation. For the functional analysis the refolded MVP channel proteins were reconstituted in giant liposomes. Using the patch clamp technique, single channels were identified at positive and negative voltages in symmetrical potassium solutions. The activation time constant at -200 mV was [tau]=440 ms. Also several channel blocking reagents were tested. Charybdotoxin, Zn²⁺, Cd²⁺ and 4AP (4- Aminopyridin) did not influence the MVP currents, but Ba²⁺ blocked the inward currents, while TEA (Tetraethylammonium) prevented channel openings at negative voltages. Obviously Ba²⁺ and TEA bind to two different sites, one accessible from the cytoplasmic and one from the intracellular side. This results indicate, that the refolded MVP protein exhibits a native-like electrophysiology and pharmacology.