The production in vivo of microcin E492 with antibacterial activity depends on salmochelin and EntF

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Microcin E492 is a channel-forming bacteriocin with modified and unmodified forms.
• Modified microcin E492 production involves enterochelin synthesis, glycosylation by MceC, and conversion to salmochelin.

Purpose of the Study:

• To investigate the molecular mechanisms underlying microcin E492 modification and maturation.
• To identify the roles of enterochelin biosynthesis genes and the Fiu receptor in microcin E492 activity.

Main Methods:

• Analysis of mceC, entB, entC, and entF mutants.
• Complementation studies with Salmonella enterica iroB.
• Assays for microcin E492 activity upon addition of exogenous compounds.
• Site-directed mutagenesis of the EntF adenylation domain.

Main Results:

• mceC mutants produced inactive microcin E492, which was restored by iroB or salmochelin.
• Cyclic salmochelin uptake in Escherichia coli primarily utilized the Fiu receptor.
• Mutants in entB and entC were complemented by pathway end products, while entF mutants remained inactive.
• The EntF adenylation domain was crucial for microcin E492 maturation, but its enzymatic activity was not essential.

Conclusions:

• The synthesis and modification of enterochelin are critical for producing active, modified microcin E492.
• The Fiu receptor plays a significant role in the uptake of salmochelin.
• Specific domains of EntF are essential for microcin E492 maturation, independent of their catalytic activity.