Figure 7.

A model for amino acid-dependent regulation of the protein levels of MepS and MepM. Under low amino acid availability, the protein level of MepS decreases through a Prc-mediated mechanism. Through an unknown regulatory mechanism, the protein level of MepM also decreases. The decreased levels of MepS and MepM may diminish the synthesis of PG. In the presence of aromatic amino acids, the protein level of MepS increases, whereas the protein level of MepM remains low. The increased protein level of MepS may slightly enhance the synthesis of PG. In the presence of aromatic amino acids and glutamate, the protein levels of both MepS and MepM increase. Increased protein levels of MepS and MepM may strongly enhance the synthesis of PG. Green and yellow circles indicate aromatic amino acids and glutamate, respectively.