Ionovation GmbH

OEP21 - A sweeping examle of use

OEP21, a pore forming membrane protein from the outer membrane of chloroplasts, was investigated using the Ionovation Compact. Proteoliposomes containing expressed PEP21 as well as membrane vesicles from the outer chloroplastic membrane were fused with the bilayer. A set of voltage ramps from -50mV applied to a bilayer containing one single copy of OEP21 is shown:

	a) Asymmetrical salt concentration of 2 M NaCl on the CIS side and 250 mM NaCl on the TRANS side.

	b) Addition of 1mM ATP to the low salt (TRANS) side. A shift in the reversal potential and a voltage dependent current block is obvious.

	c) Changing the salt gradient vice versa by perfusion of the compartments reveals a mirrored situation to a) showing that the block of ATP is reversible.

	d) Addition of 1mM ATP to the new low salt (CIS) side gives no changes in reversal potential current.


	This shows that ATP has a high affinity to OEP21 on only one side of the membrane, revealing the asymmetrical structure of this protein in a membrane, that so far was thougt to be an unspecific diffusion barrier for solutes < 10 kDa.