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Biochem Biophys Res Commun. 2001 Jul 13;285(2):550-4.

Effect of two polyamine toxins on the bacterial porin OmpF.

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1
Department of Biology and Biochemistry, 369 Science & Research Building II, University of Houston, Houston, TX 77204, USA.

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.

PMID:
11444879
DOI:
10.1006/bbrc.2001.5155
[Indexed for MEDLINE]

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