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DNA sequence analysis of the Serratia marcescens ompA gene: implications for the organisation of an enterobacterial
Abstract:
The cloned ompA gene from Serratia marcescens was fully expressed in Escherichia coli and its product correctly assembled into the outer membrane. The S. marcescens polypeptide was not functionally equivalent to the E. coli OmpA protein, which serves as a phage receptor and as a component of several colicin uptake systems. DNA sequence analysis of the gene showed that three regions of the protein likely to be exposed on the cell surface not only differed extensively from the corresponding regions of the E. coli polypeptide but also from all other sequenced OmpA proteins. It is suggested that this sequence polymorphism represents a safety mechanism by which the various enterobacterial species can avoid cross-infection by noxious agents such as phages or colicins.
Insights
The Serratia marcescens ompA gene expressed in E. coli produced a protein not functionally equivalent to E. coli OmpA. Sequence analysis revealed significant differences, suggesting a defense mechanism against phages and colicins.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The OmpA protein is a crucial outer membrane protein in enterobacteria.
- OmpA functions as a receptor for bacteriophages and is involved in colicin uptake.
- Understanding OmpA variations across species is important for microbial defense mechanisms.
Purpose of the Study:
- To investigate the expression and function of the cloned ompA gene from Serratia marcescens in Escherichia coli.
- To compare the functional equivalence and sequence characteristics of S. marcescens OmpA with E. coli OmpA.
- To explore the evolutionary implications of OmpA sequence diversity in enterobacteria.
Main Methods:
- Cloning and expression of the Serratia marcescens ompA gene in Escherichia coli.
- Analysis of the expressed protein's localization to the outer membrane.
- Functional assays to assess phage receptor and colicin uptake activity.
- DNA sequencing and comparative analysis of OmpA protein regions.
Main Results:
- The cloned ompA gene from S. marcescens was successfully expressed in E. coli, with the product assembling into the outer membrane.
- The S. marcescens OmpA protein was not functionally equivalent to the E. coli OmpA protein.
- Sequence analysis revealed extensive differences in surface-exposed regions of S. marcescens OmpA compared to E. coli OmpA and other known OmpA proteins.
Conclusions:
- The functional non-equivalence of S. marcescens OmpA in E. coli highlights species-specific adaptations.
- Sequence polymorphism in surface-exposed regions of OmpA may represent a defense mechanism against phages and colicins.
- This molecular diversity contributes to the distinct ecological niches and defense strategies of enterobacterial species.