Structure of the Z Ring-associated Protein, ZapD, Bound to the C-terminal Domain of the Tubulin-like Protein, FtsZ, Suggests Mechanism of Z Ring Stabilization through FtsZ Cross-linking

J Biol Chem. 2017 Mar 3;292(9):3740-3750. doi: 10.1074/jbc.M116.773192. Epub 2017 Jan 18.

Abstract

Cell division in most bacteria is mediated by the tubulin-like FtsZ protein, which polymerizes in a GTP-dependent manner to form the cytokinetic Z ring. A diverse repertoire of FtsZ-binding proteins affects FtsZ localization and polymerization to ensure correct Z ring formation. Many of these proteins bind the C-terminal domain (CTD) of FtsZ, which serves as a hub for FtsZ regulation. FtsZ ring-associated proteins, ZapA-D (Zaps), are important FtsZ regulatory proteins that stabilize FtsZ assembly and enhance Z ring formation by increasing lateral assembly of FtsZ protofilaments, which then form the Z ring. There are no structures of a Zap protein bound to FtsZ; therefore, how these proteins affect FtsZ polymerization has been unclear. Recent data showed ZapD binds specifically to the FtsZ CTD. Thus, to obtain insight into the ZapD-CTD interaction and how it may mediate FtsZ protofilament assembly, we determined the Escherichia coli ZapD-FtsZ CTD structure to 2.67 Å resolution. The structure shows that the CTD docks within a hydrophobic cleft in the ZapD helical domain and adopts an unusual structure composed of two turns of helix separated by a proline kink. FtsZ CTD residue Phe-377 inserts into the ZapD pocket, anchoring the CTD in place and permitting hydrophobic contacts between FtsZ residues Ile-374, Pro-375, and Leu-378 with ZapD residues Leu-74, Trp-77, Leu-91, and Leu-174. The structural findings were supported by mutagenesis coupled with biochemical and in vivo studies. The combined data suggest that ZapD acts as a molecular cross-linking reagent between FtsZ protofilaments to enhance FtsZ assembly.

Keywords: FtsZ; X-ray crystallography; ZapD; cell division; cytokinesis; electron microscopy (EM); protein-protein interaction.

MeSH terms

  • Bacterial Proteins / chemistry*
  • Cell Cycle Proteins / chemistry*
  • Cell Survival
  • Cross-Linking Reagents / chemistry
  • Crystallography, X-Ray
  • Cytoskeletal Proteins / chemistry*
  • Escherichia coli / chemistry*
  • Escherichia coli Proteins / chemistry*
  • Hydrophobic and Hydrophilic Interactions
  • Light
  • Microscopy, Electron
  • Phenotype
  • Phenylalanine / chemistry
  • Plasmids / metabolism
  • Protein Binding
  • Protein Domains
  • Protein Multimerization
  • Scattering, Radiation
  • Tubulin / chemistry*

Substances

  • Bacterial Proteins
  • Cell Cycle Proteins
  • Cross-Linking Reagents
  • Cytoskeletal Proteins
  • Escherichia coli Proteins
  • FtsZ protein, Bacteria
  • Tubulin
  • ZapD protein, E coli
  • Phenylalanine

Associated data

  • PDB/5DKO