title: Effect of two polyamine toxins on the bacterial porin OmpF.
abstract: Spermine, a polyamine based on a 12-carbon motif, is an effective inhibitor of E. coli OmpF porin. Here we study the inhibition of porin by two polyamine toxins commonly used as modulators of polyamine-sensitive channels: Philanthotoxin-433 (PhTX) from wasp venom and Joro spider toxin (JSTX). Both are highly asymmetric molecules, with at one end a 12-carbon chain polyamine targeting the molecule to the porin constriction zone, and at the other end large aromatic groups conferring to this extremity a size in the order of the OmpF constriction zone. Here we report that PhTX, but not Joro toxin, induces a high degree of flickering in the OmpF-mediated current. The effect is concentration and voltage-dependent, and greatly diminished in a mutant lacking D113 on the constriction loop, a residue previously shown to be required for spermine sensitivity. Possible reasons for the distinct sensitivity of OmpF to PhTX and Joro toxin are discussed.
authors.affiliation: Department of Biology and Biochemistry, 369 Science & Research Building II, University of Houston, Houston, TX 77204, USA.
authors.forename: A
authors.initials: A
authors.lastname: Baslé
authors.forename: A H
authors.initials: AH
authors.lastname: Delcour
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003196:Computer Graphics; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008958:Models, Molecular; D011073:Polyamines / Q000737:chemistry* / Q000494:pharmacology*; D018272:Porins / Q000737:chemistry / Q000502:physiology*; D011487:Protein Conformation; D013096:Spermine / Q000737:chemistry / Q000494:pharmacology*; D013111:Spider Venoms / Q000737:chemistry* / Q000494:pharmacology*; D014862:Wasp Venoms / Q000737:chemistry / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; C044936:JSTX spider toxin; C109237:OmpF protein; D011073:Polyamines; D018272:Porins; D013111:Spider Venoms; D014862:Wasp Venoms; D013096:Spermine; C034092:delta-philanthotoxin