Referenced in: none

Automatically associated channels: Kv2.1 , Slo1

Title: Elimination of the disulphide bridge in fragment B of diphtheria toxin: effect on membrane insertion, channel formation, and ATP binding.

Authors: H Stenmark, S Olsnes, I H Madshus

Journal, date & volume: Mol. Microbiol., 1991 Mar , 5, 595-606

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/1646374

Abstract
Active diphtheria toxin consists of two disulphide-linked fragments, termed A and B. Fragment B, which contains an internal disulphide bridge, facilitates translocation of the enzymatically active fragment A to the cytosol of eukaryotic cells. In this process cation-selective channels are formed. An in vitro translated full-length mutant lacking the internal disulphide bridge (A-58**) was functionally indistinguishable from its disulphide-containing counterpart (A-58) with respect to trypsin sensitivity, receptor binding, A-fragment translocation, and channel formation. In contrast, the B fragment of A-58** (B-36**) was slightly less trypsin resistant than the S-S-containing B fragment, B-36, and was approximately 300-fold less efficient than B-36 in permeabilizing cells. When first dialysed and then reconstituted with A fragment, B fragment without disulphide bridge yielded a less-active toxin than did wild-type B fragment. We conclude that the disulphide bridge in fragment B is not necessary for toxicity, as earlier believed, and that channel formation may play a role in membrane translocation.