Crystal structures of the OmpF porin: function in a colicin translocon
- Purdue
The OmpF porin in the Escherichia coli outer membrane (OM) is required for the cytotoxic action of group A colicins, which are proposed to insert their translocation and active domains through OmpF pores. A crystal structure was sought of OmpF with an inserted colicin segment. A 1.6 {angstrom} OmpF structure, obtained from crystals formed in 1 M Mg{sup 2+}, has one Mg{sup 2+} bound in the selectivity filter between Asp113 and Glu117 of loop 3. Co-crystallization of OmpF with the unfolded 83 residue glycine-rich N-terminal segment of colicin E3 (T83) that occludes OmpF ion channels yielded a 3.0 {angstrom} structure with inserted T83, which was obtained without Mg{sup 2+} as was T83 binding to OmpF. The incremental electron density could be modelled as an extended poly-glycine peptide of at least seven residues. It overlapped the Mg{sup 2+} binding site obtained without T83, explaining the absence of peptide binding in the presence of Mg{sup 2+}. Involvement of OmpF in colicin passage through the OM was further documented by immuno-extraction of an OM complex, the colicin translocon, consisting of colicin E3, BtuB and OmpF.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006860
- Journal Information:
- EMBO J., Vol. 27, Issue (15) ; 2008; ISSN 0261-4189
- Country of Publication:
- United States
- Language:
- ENGLISH
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