Membrane-bound lytic endotransglycosylase in Escherichia coli

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• The bacterial cell envelope, particularly the murein sacculus, is crucial for bacterial integrity and survival.
• Lytic transglycosylases are enzymes involved in peptidoglycan remodeling, essential for cell growth and division.

Purpose of the Study:

• To characterize a newly identified gene, emtA, encoding a membrane-bound lytic transglycosylase in E. coli.
• To elucidate the enzymatic activity and potential function of the EmtA protein.

Main Methods:

• Gene mapping of emtA on the E. coli chromosome.
• Overexpression of the emtA gene.
• Enzymatic assays using isolated murein glycan strands.
• Analysis of hydrolysis products to determine enzyme specificity.

Main Results:

• The emtA gene was localized to the E. coli chromosome at 26.7 min.
• EmtA was identified as a 22kDa lipoprotein.
• Overexpression did not cause bacteriolysis in vivo.
• EmtA demonstrated endospecific hydrolysis of murein glycan strands, producing tetra- and hexasaccharides with 1,6-anhydromuramic acid, characteristic of lytic transglycosylases.

Conclusions:

• EmtA functions as a lytic transglycosylase, cleaving murein glycan strands.
• Potential roles for EmtA include formatting nascent murein or creating pores for export of bulky compounds across the cell envelope.