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Characterization of a porin from the outer membrane of Vibrio anguillarum
Abstract:
The outer membranes of the 10 serovars of Vibrio anguillarum showed a common major protein with a size of around 40 kDa. Antibodies against the major outer membrane protein (MOMP) of V. anguillarum AO18 (serovar O1) cross-reacted with the MOMPs of all the other serovars but not with the outer membrane proteins of Escherichia coli. The MOMP of V. anguillarum serovar O1 was isolated, reconstituted to two-dimensional crystals, and structurally characterized by electron microscopy and image processing. The unit cell structure of the crystalline MOMP, as well as the secondary structure composition of the protein with a high amount of beta-structure, is strongly reminiscent of that of bacterial porins. The functional properties of the pores were investigated by conductance measurements with the MOMP reconstituted in planar lipid membranes. The V. anguillarum MOMP is characterized by a relatively weak cation selectivity and a moderate surface charge, and it shows voltage-dependent conductance effects. The MOMP is functionally similar to OmpF from E. coli, and it can be classified as a general diffusion porin.
Insights
The major outer membrane protein (MOMP) of Vibrio anguillarum is common across serovars and structurally similar to bacterial porins. Functional studies reveal it acts as a general diffusion porin with voltage-dependent conductance.
Area of Science:
- Microbiology
- Structural Biology
- Biophysics
Background:
- Vibrio anguillarum is a significant fish pathogen.
- Outer membrane proteins (OMPs) play crucial roles in bacterial structure and function.
- Identifying conserved OMPs can aid in understanding bacterial pathogenesis and developing diagnostics or therapeutics.
Purpose of the Study:
- To characterize the major outer membrane protein (MOMP) of Vibrio anguillarum.
- To determine the structural and functional properties of the MOMP.
- To compare the MOMP to known porins from other bacteria.
Main Methods:
- Immunological cross-reactivity assays using antibodies against V. anguillarum MOMP.
- Isolation and purification of the MOMP.
- Reconstitution into two-dimensional crystals for structural analysis via electron microscopy and image processing.
- Functional characterization using conductance measurements in planar lipid membranes.
Main Results:
- A common 40 kDa MOMP was identified across 10 Vibrio anguillarum serovars.
- Antibodies against serovar O1 MOMP cross-reacted with MOMPs from other serovars, but not with E. coli OMPs.
- Structural analysis revealed a high beta-structure content, characteristic of bacterial porins.
- Functional studies showed the MOMP exhibits weak cation selectivity, moderate surface charge, and voltage-dependent conductance, classifying it as a general diffusion porin similar to E. coli OmpF.
Conclusions:
- The Vibrio anguillarum MOMP is a conserved protein across different serovars.
- The MOMP possesses structural and functional characteristics of a bacterial porin.
- Its classification as a general diffusion porin provides insights into nutrient and ion transport in V. anguillarum.