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Major heat-modifiable outer membrane protein in gram-negative bacteria: comparison with the ompA protein of
Abstract:
The outer membranes of several strains of Escherichia coli, other enteric bacteria, and a variety of nonenteric gram-negative bacteria all contain a major heat-modifiable protein similar to the OmpA protein of E. coli K-12. The heat-modifiable proteins from these bacteria resemble the K-12 protein in molecular weight, in preferential release from the outer membrane by sodium dodecyl sulfate in the presence of Mg2+, and in characteristic cleavage by proteases to yield a smaller fragment which remains membrane bound. Antiserum directed against the K-12 protein precipitated the heat-modifiable protein from all strains of Enterobacteriaceae, and chemical comparison by isoelectric focusing, cyanogen bromide cleavage profiles, and proteolytic peptide analysis indicated that the proteins from the various enteric bacteria were nearly identical in primary structure. The heat-modifiable proteins from bacteria phylogenically distant from E. coli shared many of the properties of the E. coli protein but were chemically distinct. Thus, it appears that the structure (and, presumably, the function) of the heat-modifiable protein of gram-negative bacteria is strongly conserved during evolution.
Insights
Gram-negative bacteria outer membranes share a conserved heat-modifiable protein, similar to Escherichia coli OmpA. This protein
Area of Science:
- Microbiology
- Bacterial Outer Membrane Proteins
- Molecular Biology
Background:
- Gram-negative bacteria possess a major heat-modifiable protein in their outer membranes.
- This protein is structurally and functionally analogous to the OmpA protein found in Escherichia coli K-12.
Purpose of the Study:
- To investigate the conservation of the heat-modifiable outer membrane protein across diverse bacterial species.
- To compare the structural and chemical properties of this protein in Escherichia coli and other gram-negative bacteria.
Main Methods:
- Comparative analysis of heat-modifiable proteins from various enteric and nonenteric gram-negative bacteria.
- Techniques included molecular weight determination, sodium dodecyl sulfate (SDS) release assays, protease cleavage analysis, antiserum precipitation, isoelectric focusing, cyanogen bromide cleavage profiling, and proteolytic peptide analysis.
Main Results:
- Heat-modifiable proteins from Enterobacteriaceae were nearly identical in primary structure to the E. coli K-12 OmpA protein.
- Proteins from phylogenetically distant bacteria shared properties but were chemically distinct.
- The protein exhibited characteristic release from the outer membrane and protease cleavage patterns.
Conclusions:
- The structure and function of the heat-modifiable outer membrane protein are highly conserved across gram-negative bacteria.
- Evolutionary conservation suggests significant functional importance for this major outer membrane protein.