| Symmetric division of Gram-negative bacteria depends on the combined action of three proteins that ensure correct positioning of the cell division septum; namely, MinC, MinD and MinE. To achieve this function, MinC and MinD form a membrane-bound complex that blocks cell division at all potential sites. Opposing this inhibition is MinE, which interacts with MinD via its N-terminal anti-MinCD domain to site-specifically counter the action of the MinCD complex. The anti-MinCD domain has been proposed to bind MinD in a helical conformation, however, little is actually known about the structure of this functionally critical region. In order to understand how MinE can perform its anti-MinCD function, we have therefore investigated the structural properties of the full-length MinE from N. gonorrhoeae. Results from solution NMR show that, in contrast to previous models, parts of the anti-MinCD domain are stably folded with many functionally important residues forming part of a beta-structure. In addition, this structure may be stabilized by interactions with the C-terminal topological specificity domain, since mutations made in one domain led to NMR spectral changes in both domains. The inactive MinE mutant L22D showed even larger evidence of structural perturbations, with significant destabilization of the entire MinE structure. Overall, these results suggest an intimate structural association between the anti-MinCD and topological specificity domains raising the possibility that the functional properties of the two domains could be modulated through this interaction. |
