Effect of cholesterol on phospholipid, RNA, and protein synthesis in Mycoplasma capricolum

The regulatory role of cholesterol on phospholipid, RNA and protein synthesis was investigated in Mycoplasma capricolum. The addition of 2 micrograms/ml of cholesterol to cells growing slowly on lanosterol (10 micrograms/ml) caused an early stimulation of unsaturated phospholipid synthesis followed by a later stimulation of RNA and protein synthesis. Epicoprostanol, a cholesterol antagonist, sequentially inhibited these three processes. Phospholipid served as the acyl donor for the acylation of membrane proteins. Membrane-bound cholesterol correlated with a decrease in the amount of [3H]amino acids and an increase in the amount of [3H]oleate found in two membrane proteins (MW 78 kDa and 26 kDa). Taken together, the results suggest that a small amount of membrane-associated cholesterol serves as a signal for membrane biogenesis and, in turn, macromolecular synthesis and cell growth.