General Information

Database accession: MF2120011

Name: Cell division factor ZapB

PDB ID: 2jee PDB

Experimental method: X-ray (2.8 Å)

Assembly: homodimer

Source organism: Escherichia coli

Primer publication of the structure:

Ebersbach G, Galli E, Møller-Jensen J, Löwe J, Gerdes K
Novel coiled-coil cell division factor ZapB stimulates Z ring assembly and cell division.
(2008) Mol. Microbiol. 68: 720-35

PMID: 18394147 PubMed

Abstract:

Formation of the Z ring is the first known event in bacterial cell division. However, it is not yet known how the assembly and contraction of the Z ring are regulated. Here, we identify a novel cell division factor ZapB in Escherichia coli that simultaneously stimulates Z ring assembly and cell division. Deletion of zapB resulted in delayed cell division and the formation of ectopic Z rings and spirals, whereas overexpression of ZapB resulted in nucleoid condensation and aberrant cell divisions. Localization of ZapB to the divisome depended on FtsZ but not FtsA, ZipA or FtsI, and ZapB interacted with FtsZ in a bacterial two-hybrid analysis. The simultaneous inactivation of FtsA and ZipA prevented Z ring assembly and ZapB localization. Time lapse microscopy showed that ZapB-GFP is present at mid-cell in a pattern very similar to that of FtsZ. Cells carrying a zapB deletion and the ftsZ84(ts) allele exhibited a synthetic sick phenotype and aberrant cell divisions. The crystal structure showed that ZapB exists as a dimer that is 100% coiled-coil. In vitro, ZapB self-assembled into long filaments and bundles. These results raise the possibility that ZapB stimulates Z ring formation directly via its capacity to self-assemble into larger structures.

Function and Biology Annotations from the GeneOntology database. Only terms that fit at least two of the interacting proteins are shown.

Molecular function:

identical protein binding Interacting selectively and non-covalently with an identical protein or proteins. GeneOntology

Biological process:

FtsZ-dependent cytokinesis A cytokinesis process that involves a set of conserved proteins including FtsZ, and results in the formation of two similarly sized and shaped cells. GeneOntology

cell septum assembly The assembly and arrangement of a cellular component that is composed of peptidoglycan and often chitin in addition to other materials and usually forms perpendicular to the long axis of a cell or hypha. It grows centripetally from the cell wall to the center of the cell and often functions in the compartmentalization of a cell into two daughter cells. GeneOntology

Cellular component:

cytosol The part of the cytoplasm that does not contain organelles but which does contain other particulate matter, such as protein complexes. GeneOntology

cell division site The eventual plane of cell division (also known as cell cleavage or cytokinesis) in a dividing cell. In Eukaryotes, the cleavage apparatus, composed of septin structures and the actomyosin contractile ring, forms along this plane, and the mitotic, or meiotic, spindle is aligned perpendicular to the division plane. In bacteria, the cell division site is generally located at mid-cell and is the site at which the cytoskeletal structure, the Z-ring, assembles. GeneOntology

Structure Summary Structural annotations of the participating protein chains.

Entry contents: 2 distinct polypeptide molecules

Chains: A, B

Notes: Chains C and D were removed as chains A and B represent the biologically relevant dimer.

Number of unique protein segments: 1

Chain A

Name: Cell division protein ZapB

Source organism: Escherichia coli

Length: 81 residues

Sequence:Sequence according to PDB SEQRESMTMSLEVFEKLEAKVQQAIDTITLLQMEIEELKEKNNSLSQEVQNAQHQREELERENNHLKEQQNGWQERLQALLGRMEEV

UniProtKB AC: P0AF36 (positions: 1-81) UniProt Coverage: 100%

UniRef90 AC: UniRef90_A7ZUE3 (positions: 1-81) UniRef90

Chain B

Name: Cell division protein ZapB

Source organism: Escherichia coli

Length: 81 residues

Sequence:Sequence according to PDB SEQRESMTMSLEVFEKLEAKVQQAIDTITLLQMEIEELKEKNNSLSQEVQNAQHQREELERENNHLKEQQNGWQERLQALLGRMEEV

UniProtKB AC: P0AF36 (positions: 1-81) UniProt Coverage: 100%

UniRef90 AC: UniRef90_A7ZUE3 (positions: 1-81) UniRef90

Evidence Evidence demonstrating that the participating proteins are unstructured prior to the interaction and their folding is coupled to binding.

Complex evidence:

The subunits in the structure are bound via coiled coil interactions (PMID: 18394147). Coiled coils are highly versatile folding units (PMID: 11166216), where the formation of the structure and the interaction between subunits is almost ubiquitously linked. This cooperative nature of binding and folding that results in a two-step process has been demonstrated for coiled coils with varying oligomeric state from dimers (PMID: 9811815) and trimers (PMID: 10933510) up to heptamers (PMID: 17030805). While the interaction and folding are linked, in certain cases there can be significant residual structure before association (PMID: 8401212). However, these residual structural elements usually encompass 1-2 turns of helices that serve as a 'nucleation site' driving interaction and helix formation (zipping up) (PMID: 17438295), thus even in these cases monomeric coiled coil subunits cannot be considered to have a stable structure.

Related Structure(s) Structures from the PDB that contain the same number of proteins, and the proteins from the two structures show a sufficient degree of pairwise similarity, i.e. they belong to the same UniRef90 cluster (the full proteins exhibit at least 90% sequence identity) and convey roughly the same region to their respective interactions (the two regions from the two proteins share a minimum of 70% overlap).

No related structure was found in the Protein Data Bank.

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