Initial membrane reaction in peptidoglycan synthesis: perturbation of lipid-phospho-N-acetylmuramyl-pentapeptide translocase interactions by n-butanol

Abstract

Phospho-N-acetylmuramyl-pentapeptide translocase, the initial membrane enzyme in the biosynthesis of peptidoglycan, requires a lipid microenvironment for function. n-Butanol was reversibly intercalated into membranes to perturb the hydrophobic interactions in this microenvironment in order to define further the role of lipid. In the concentration range for maximal stimulation of enzymic activity (0.12-0.18 M), n-butanol causes a 40% decrease in the fluorescence emission of the dansylated product, undecaprenyl diphosphate-(N epsilon-dansyl)pentapeptide. Since no change in emission maximum occurs below 22 degrees C in the presence of 0.12 M n-butanol, it is concluded that intercalation of this alkanol causes an increase in fluidity. Above 22 degrees C this concentration of n-butanol causes both a decrease in the fluorescence emission and a red shift in the emission maximum. It is concluded that a polarity change as well as fluidity change occurs above 22 degrees C. n-Butanol also causes a significant change in the phase transition experienced by the dansylated lipid product. Thus, it is possible with n-alkanols, e.g. n-butanol, to perturb lipid-translocase interactions resulting in an increase in fluidity in the microenvironment of the enzyme. This change in fluidity correlates with a stimulation of enzymic activity.