A mechanism for toxin insertion into membranes is suggested by the crystal structure of the channel-forming domain of colicin E1
Elkins, P., Bunker, A., Cramer, W.A., Stauffacher, C.V.(1997) Structure 5: 443-458
- PubMed: 9083117 
- DOI: https://doi.org/10.1016/s0969-2126(97)00200-1
- Primary Citation of Related Structures:  
2I88 - PubMed Abstract: 
Channel-forming colicins, including colicin E1, are a sub-family of bacteriocins. The toxic action of colicin E1 is derived from its ability to form a voltage-gated channel, which causes depolarization of the cytoplasmic membrane of sensitive Escherichia coli cells. In this process, the toxin-like colicin E1 molecule must undergo a substantial structural transition from a soluble state, in which it binds the target cell, to a membrane-bound state. Details of the structural changes that accompany this conversion may be directly applicable to other channel-forming toxins, as well as to the mechanism by which proteins insert into or cross membranes.
Organizational Affiliation: 
Protein Engineering, Department Genentech, Inc. 460 Pt. San Bruno Blvd, South San Francisco, CA 94080, USA.