Subcellular targeting of and protein -protein interaction within the bacterial cell division complex
Bacterial cell division is a complex process that relies on the intricate timing and placement of the FtsZ ring. FtsZ, the prokaryotic homologue of tubulin, assembles into the FtsZ ring at the cell midpoint and is proposed to provide a scaffold upon which the remaining cell division components localize. The resulting putative protein complex or divisome is required for the synthesis of the division septum and subsequent formation of new cell poles. Although most of the components of the cell division machinery have likely been identified, how this multi-subunit complex is assembled within the membrane, and the precise role of each protein, has remained elusive. In addition, the mechanism for selection of the division plane between daughter chromosomes at the cell midpoint is also not well understood. Using a novel polar recruitment assay, we found that FtsA can recruit at least two late septation proteins, FtsI and FtsN, to the cell poles independently of FtsZ rings. Moreover, a unique structural domain of FtsA, domain 1c, is sufficient for this recruitment but not required for the ability of FtsA to localize to FtsZ rings. By conducting immuno-precipitation experiments, we were also able to identify a specific binary interaction between FtsZ and FtsE, part of a putative ABC transporter. The MinCDE proteins help to select cell division sites in normal cylindrical E. coli by oscillating along the long axis, preventing unwanted polar divisions. To determine how the Min system might function in three dimensional space, we investigated its role in a round-cell rodA mutant. Round cells lacking MinCDE were viable, but growth, morphology and positioning of cell division sites were abnormal relative to Min+ cells. In round cells with a long axis, a green fluorescent protein (GFP) fusion to MinD almost always oscillated parallel to the long axis. However, round or irregularly shaped cells exhibited MinD movement to and from multiple sites on the cell surface. A MinE-GFP fusion also exhibited similar behavior. These results indicate that the Min proteins can potentially localize anywhere in the cell but tend to move a certain maximum distance from their previous assembly site.
Corbin, Brian Dale, "Subcellular targeting of and protein -protein interaction within the bacterial cell division complex" (2006). Texas Medical Center Dissertations (via ProQuest). AAI3209529.