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The final step of peptidoglycan subunit assembly in Escherichia coli occurs in the cytoplasm
1Laboratoire de Biochimie Moléculaire et Cellulaire, URA 1131, Université Paris-Sud, Orsay, France.
Abstract:
The murG gene of Escherichia coli encodes the N-acetylglucosaminyltransferase responsible for the final step in the formation of the lipid-linked disaccharide-pentapeptide subunit of peptidoglycan. Using trypsin to probe maxicell spheroplasts, we show that this enzyme is peripherally associated with the inner face of the cytoplasmic membrane. Therefore, the peptidoglycan subunit is completely assembled before it traverses the cytoplasmic membrane.
Insights
The murG gene enzyme in Escherichia coli is key for peptidoglycan formation. This enzyme attaches to the inner cytoplasmic membrane, indicating peptidoglycan assembly completes before crossing it.
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Peptidoglycan is a crucial component of the bacterial cell wall, essential for structural integrity.
- The synthesis of peptidoglycan involves a complex series of enzymatic steps.
- The murG gene product is known to catalyze the final enzymatic step in the formation of the peptidoglycan subunit.
Purpose of the Study:
- To determine the cellular localization of the N-acetylglucosaminyltransferase enzyme encoded by the murG gene.
- To elucidate the stage at which the peptidoglycan subunit is assembled relative to its transport across the cytoplasmic membrane.
Main Methods:
- Utilized maxicell spheroplasts of Escherichia coli for biochemical analysis.
- Employed trypsin digestion to probe the association of the murG gene product with cellular membranes.
Main Results:
- The N-acetylglucosaminyltransferase (MurG) enzyme is peripherally associated with the cytoplasmic membrane.
- Specifically, the enzyme is located on the inner face of the cytoplasmic membrane.
- This localization indicates that the lipid-linked disaccharide-pentapeptide subunit is fully assembled before translocation.
Conclusions:
- The MurG enzyme's localization confirms the complete assembly of the peptidoglycan subunit within the cytoplasm.
- Peptidoglycan subunit assembly precedes its passage across the cytoplasmic membrane.
- This finding provides critical insight into the spatial organization of peptidoglycan biosynthesis in Escherichia coli.