ROLE OF THE CONSTRICTION LOOP IN THE GATING OF OUTER-MEMBRANE PORIN PHOE OF ESCHERICHIA-COLI

Porins form voltage-gated channels in the bacterial outer membrane, Th ese proteins are composed of three identical submits, each forming a 1 6-stranded beta-barrel, In this study, the role in voltage gating of a loop that forms a constriction within the pore was studied, The chann el characteristics of mutant PhoE porins, in which the tip of the cons triction loop was connected to the barrel wall, were determined, Where as the properties of several mutant channels were changed, all of thes e channels could still be closed at high potential, showing that a gro ss movement of the constriction loop within the channel is not implica ted in voltage gating. (C) 1997 Federation of European Biochemical Soc ieties.