Appropriation of the MinD protein-interaction motif by the dimeric interface of the bacterial cell division regulator MinE

Abstract

MinE is required for the dynamic oscillation of Min proteins that restricts formation of the cytokinetic septum to the midpoint of the cell in gram negative bacteria. Critical for this oscillation is MinD-binding by MinE to stimulate MinD ATP hydrolysis, a function that had been assigned to the first ∼30 residues in MinE. Previous models based on the structure of an autonomously folded dimeric C-terminal fragment suggested that the N-terminal domain is freely accessible for interactions with MinD. We report here the solution NMR structure of the full-length MinE dimer from Neisseria gonorrhoeae, with two parts of the N-terminal domain forming an integral part of the dimerization interface. Unexpectedly, solvent accessibility is highly restricted for residues that were previously hypothesized to directly interact with MinD. To delineate the true MinD-binding region, in vitro assays for MinE-stimulated MinD activity were performed. The relative MinD-binding affinities obtained for full-length and N-terminal peptides from MinE demonstrated that residues that are buried in the dimeric interface nonetheless participate in direct interactions with MinD. According to results from NMR spin relaxation experiments, access to these buried residues may be facilitated by the presence of conformational exchange. We suggest that this concealment of MinD-binding residues by the MinE dimeric interface provides a mechanism for prevention of nonspecific interactions, particularly with the lipid membrane, to allow the free diffusion of MinE that is critical for Min protein oscillation.protein structure | conformational dynamics | protein-protein interactions | ATPase

MinE conformational dynamics regulate membrane binding, MinD interaction, and Min oscillation

“…It also rescued MinE D45A . The I74 residue is located in β3 and is involved in tethering the MTS to the six-stranded β-sheet (18) (Fig. 1).…”

“…. The structure of MinE from Neisseria gonorrhoeae (NgMinE) was determined by NMR spectroscopy (18). Interestingly, NgMinE…”

“…The latent conformation is a 6β-stranded structure that diffuses in the cytoplasm because the segments of MinE that interact with MinD (β1 strand at the dimer interface) and the membrane (N-terminal amphipathic helices also called membrane targeting sequences, MTS) are masked. In contrast, the active conformation consists of a 4β-stranded structure with the MTS bound to the membrane and the released β1 strand and part of the loop region (residues [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] converted to an alpha helix bound to MinD (Fig. 1).…”

“…The latent form of MinE has a hydrophobic core with the sixstranded β-sheet sandwiched between the MTS on one face and two long antiparallel helices (αB) forming a coiled coil on the opposite face (18) (Fig. 1).…”

Membrane-bound MinDE complex acts as a toggle switch that drives Min oscillation coupled to cytoplasmic depletion of MinD

“…MinE also has an MTS essential for the spatial regulation of cell division (17). Structural studies suggest that, in solution, the MTS and the adjacent MinDinteraction domain of MinE are sequestered in the hydrophobic core of the dimer (18,19). Thus, under physiological conditions, MinE does not interact with MinD in the absence of membrane and shows only a weak affinity for E. coli membrane in the absence of MinD (17).…”