Effects of Glycerol Deprivation on Macromolecular Synthesis

Cells deprived of glycerol go through one slow cell division cycle. This may be due to effects on DNA synthesis, since in the case of germinating spores of B. subtilis, mutant spores deprived of glycerol do not divide even once. However, the replication of the chromosome of the germinating spore is found to terminate somewhere in the middle of its replication cycle.  

Since it was observed that protein synthesis continues after the cessation of net lipid synthesis, it was of interest to determine whether the synthesis of membrane proteins continues under these circumstances. Membranes isolated from cells deprived of glycerol show an increase in protein content, but no increase in lipid content, indicating that membrane 

Membranes prepared from Protein (mg) Lipid P (jig) Lipid (mg) 

B42 at zero time B42 glycerol-deprived for 60 min B42 glycerol-supplemented for 60 min 

The results cited above indicate that there is no regulation of the synthesis of membrane proteins by the composition of the cell membrane. We know that the synthesis of some membrane proteins, such as the lac-transport protein in E. coli, is controlled at the level of transcription by the normal regulatory processes of the lac operon. The same type of control may apply for other membrane proteins as well. In other words, their synthesis is controlled by regulatory processes that are independent of the state of the membrane, but dependent upon other physiological parameters of the cell, such as positive and negative transcriptional controls, catabolite repression, the general level of energy metabolism and the availability of compounds necessary for protein synthesis. 

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