DELETION ANALYSIS OF GENE MINE WHICH ENCODES THE TOPOLOGICAL SPECIFICITY FACTOR OF CELL-DIVISION IN ESCHERICHIA-COLI

Division inhibition caused by the minCD gene products of Escherichia coli is suppressed specifically at mid-cell by MinE protein expressed at physiological levels. Excess MinE allows division to take place also at the poles, leading to a minicell-forming (Min(-)) phenotype, In order to investigate the basis of this topological specificity, we have analysed the ability of truncated derivatives of MinE to suppress either minCD-dependent division inhibition in a chromosomal Delta(minB) background, or the division inhibition exerted by MinCD at the cell poles in a minB(+) strain. Our results indicate that these two effects are not mediated by identical interactions of MinE protein, In addition, gel filtration and the yeast two-hybrid system indicated that MinE interacts with itself by means of its central segment, Taken together, our results favour a model in which wild-type MinE dimer molecules direct the division inhibitor molecules to the cell poles, thus preventing polar divisions and allowing non-polar sites to divide. This model explains how excess MinE, or an excess of certain MinE derivatives which prevent the accumulation of the division inhibitor at the poles, can confer a Min(-) phenotype in a minB(+) strain.