Role of MinD-membrane association in Min protein interactions.

Division site placement in Escherichia coli involves interactions of the MinD protein with MinC and MinE and with other MinD molecules to form membrane-associated polymeric structures. In this work, as part of a study of these interactions, we established that heterologous membrane-associated proteins such as MinD can be targeted to the yeast nuclear membrane, dependent only on the presence of a membrane-binding domain and a nuclear targeting sequence. Targeting to the nuclear membrane was equally effective using the intrinsic MinD membrane-targeting domain or the completely unrelated membrane-targeting domain of cytochrome b(5). The chimeric proteins differing in their membrane-targeting sequences were then used to establish the roles of membrane association and specificity of the membrane anchor in MinD interactions, using the yeast two-hybrid system. The chimeric proteins were also used to show that the membrane association of MinD and MinE in E. coli cells had no specificity for the membrane anchor, whereas formation of MinDE polar zones and MinE rings required the presence of the native MinD membrane-targeting sequence.