Effect of glycerol on the affinity of DnaA protein for ATP in the presence of cardiolipin

Acidic phospholipids, such as cardiolipin, decrease the affinity of DnaA protein for adenine nucleotides and can activate the inactive form of DnaA protein in vitro. In this study, we examined the effect of glycerol on the affinity of DnaA protein for ATP in the presence of cardiolipin. High concentrations of glycerol (34%) restored the affinity of DnaA protein for ATP, which was decreased by cardiolipin. Glycerol inhibited the binding of cardiolipin with DnaA protein. Glycerol had little effect on membrane fluidity, which is essential for the interaction between cardiolipin and DnaA protein, whereas it increased the K(d) value of DnaA protein for ATP in the absence of cardiolipin. These results suggest that glycerol causes DnaA protein to become insensitive as to the interaction with cardiolipin by changing the conformation of the protein without altering the physical nature of the phospholipid.