Studies on human porin XIX: zinc ions reduce the voltage-dependence of human type-1 porin integrated in artificial planar lipid bilayers; barium ions do not.

We report on the first data concerning the effects of ionic zinc or barium on human type-1 porin. The channel enriched as mature protein from B-lymphocyte crude membranes was integrated into artificial planar lipid bilayers and both agonists were applied as their chloride salts at 100 microM. Relative conductance was measured from -80 to 80 mV. The presence of Zn2+ resulted in a distinct reduction of the voltage dependence of the channel, the effect appearing to be symmetric. The addition of Ba2+ did not produce any measurable effect on human porin. According to our knowledge we present the first results on the interaction of bivalent metal ions and eukaryotic type-1 porin. The putative physiological relevance of the data is discussed.