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On the mechanism and pathway of colicin import across the E. Coli outer membrane

Stanislav D Zakharov1, William A Cramer

  • 1Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907-1392, USA.

Frontiers in Bioscience : a Journal and Virtual Library
|February 24, 2004
PubMed

Insights

Colicins use two outer membrane protein receptors for cell entry. New structural and spectroscopic data reveal how BtuB and OmpF form a translocon for colicin E3 translocation.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Colicins and phages exploit outer membrane proteins (Omps) for cellular entry.
  • Several colicins require two Omps for cytotoxicity, but the translocation mechanism remains unclear.
  • Key questions involve initial binding, unfolding, energy sources, and interactions with periplasmic proteins.

Purpose of the Study:

  • To elucidate the mechanism of colicin translocation across the outer membrane.
  • To investigate the role of two outer membrane receptors in colicin E3 entry.
  • To propose a model for the BtuB-OmpF translocon.

Main Methods:

  • 3D crystal structure determination of BtuB and the BtuB-R135 complex.
  • Spectroscopic analysis of R135-BtuB interactions.
  • Electrophysiological studies of colicin E3-OmpF interactions.

Main Results:

  • 3D structures provided insights into BtuB and colicin E3 receptor binding domain (R135) interactions.
  • Spectroscopic and electrophysiological data revealed BtuB-OmpF interactions.
  • A model for a two-receptor translocon (BtuB-OmpF) for colicin E3 was proposed.

Conclusions:

  • The BtuB-OmpF complex functions as an outer membrane translocon for colicin E3.
  • Structural and functional data support a two-receptor model for colicin translocation.
  • This work advances understanding of colicin-host interactions and outer membrane transport.

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