The final step of peptidoglycan subunit assembly in Escherichia coli occurs in the cytoplasm.

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.