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Structural and Functional Analysis of Multiprotein Complexes Required for Colicin Translocation

University of Nottingham
Start date
End date
To provide a competitive advantage for nutrient acquisition or colonisation of new environments many Escherichia coli cells secrete a ribosomally synthesised bactericidal colicin to kill closely related non-immune bacteria. The majority of colicins exert their lethality by a C-terminal cytotoxic domain that either causes membrane depolarisation of the cytoplasmic membrane (the pore-forming colicins) or degradation of RNA or DNA (the enzymatic colicins). Import of the cytotoxic domain requires the co-operation of two other separate structural domains. The first is a centrally located receptor binding domain that targets the colicin to the bacterial outer membrane and the second is an N-terminal translocation domain that makes contact with several proteins in the outer membrane and periplasmic space of the cell, and is believed to act as a signalling mechanism for entry of the cytotoxic domain. Colicin translocation can occur via the tol-dependent translocation system which is used by Group A colicins such as the enzymatic E colicins and requires a specific pentapeptide sequence in the N- terminal translocation region (TolB box), that is intrinsically disordered and is known to interact with the periplasmic protein TolB. In contrast the pore-forming colicin A has a TolA box in the translocation domain that interacts with TolA, as well as having a TolB box.

In this project we will carry out structural and functional analysis of the protein-protein interactions of colicin A and colicin E9 with all the translocation proteins in order to better understand the translocation process.

Funding Source
Biotechnology and Biological Sciences Research Council
Project number
Natural Toxins
Bacterial Pathogens
Escherichia coli