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Sequence analysis of the four plasmid genes required to produce the circular peptide antibiotic microcin J25
J O Solbiati1, M Ciaccio, R N Farías
1Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán), Argentina.
Abstract:
A 4.8-kb plasmid region carrying the four genes mcjABCD necessary for production of and immunity to the cyclic peptide antibiotic microcin J25 (MccJ25) has been sequenced. mcjA encodes the primary structure of MccJ25 as a precursor endowed with an N-terminal extension of 37 amino acids. The products of mcjB and mcjC are thought to be involved in microcin maturation, which implies cleavage of McjA and head-tail linkage of the 21-residue pro-MccJ25. The predicted McjD polypeptide, which is highly similar to several ABC exporters, was found to be required for MccJ25 secretion, thus explaining its ability to confer immunity to MccJ25.
Insights
The genes mcjABCD are essential for producing the antibiotic microcin J25 (MccJ25) and conferring immunity. Sequencing revealed mcjA encodes the precursor, while mcjB, mcjC, and mcjD are involved in maturation and secretion.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Microcin J25 (MccJ25) is a cyclic peptide antibiotic.
- The genetic basis for MccJ25 production and immunity was previously unknown.
Purpose of the Study:
- To sequence the plasmid region containing genes responsible for MccJ25 production and immunity.
- To elucidate the roles of individual genes in the MccJ25 biosynthesis pathway.
Main Methods:
- Plasmid DNA sequencing of the 4.8-kb region containing mcjABCD.
- Bioinformatic analysis of gene products and their predicted functions.
Main Results:
- The mcjABCD gene cluster was sequenced, revealing genes essential for MccJ25 production and immunity.
- mcjA encodes the MccJ25 precursor with an N-terminal extension.
- mcjB and mcjC are implicated in precursor processing and head-tail linkage.
- mcjD, an ABC transporter, is crucial for MccJ25 secretion and immunity.
Conclusions:
- The mcjABCD genes provide a complete system for MccJ25 biosynthesis, maturation, secretion, and immunity.
- The McjD protein plays a dual role in exporting MccJ25 and protecting the producing cell.