Center for Structural Genomics of Infectious Diseases

Structure of IDP90225

Structure of a putative YscO homolog CT670 from Chlamydia trachomatis

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CSGID target: IDP90225
PDB Id: 3K29 (NCBI MMDB)
Authors: Lam, R., Singer, A., Skarina, T., Onopriyenko, O., Bochkarev, A., Brunzelle, J.S., Edwards, A.M., Anderson, W.F., Chirgadze, N.Y., Savchenko, A.
Responsible person: Alexander Singer
Responsible lab: University of Toronto
Deposition Date: Sep 29, 2009
Release Date: Oct 13, 2009

Annotation

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Description: Gram-negative pathogens exert a much of their virulence through the secretion of toxins, termed effectors, through the type III secretion system. This involves the multi-step assembly of a nanomachine, termed the “type III secretion apparatus” (T3SA), to form a “needle” spanning the bacterial and host membranes, and through this needle, the effectors are passed from the bacteria to the host. Assembly of the T3SA is related to assembly of the bacterial flagellum, as a number of proteins involved in flagellar assembly have counterparts in the type III secretion system. The YscO family of proteins are known to be involved in assembly of the type III secretion system and is thought to be related to the flagellar protein FliJ. Its role in assembly of the type III apparatus is unclear, but has been shown to interact with the “molecular ruler” YscP which designates the needle length. In addition, both YscO and FliJ have been shown to bind type III and flagellar chaperones, respectively, following release of cargo by these chaperones. We report the structure of CT670, the homologue of YscO from Chlamydia trachomatis, to 2 Å. This is the first reported structure of a YscO or FliJ protein, and its structure is revealed to be a coiled-coil containing almost exclusively 2 very long helices over its 168 residues. The first helix is “straightened” by Pro5 at the N-terminus, and this conformation is held by the insertion of the Tyr4 ring into a hydrophobic patch in the middle of the coiled coil. Overall the resulting structure is highly elongated and predicted to be monomeric, with patches of electropositive and electronegative potential over its length. This protein has been shown to bind to its YscP homologue, CT671; the molecular mechanism for this interaction or its interaction with type III chaperones has yet to be determined. The overall structure of CT670 is an elongated coiled coil with two very large helices. Based on its crystal packing interactions, this protein is expected to be monomeric in solution.
Functional assignment: Type III Secretion System Assembly

Slides:

Asymmetric unit

Biological unit

B-factors distribution

B-factors distribution on the surface

Homolog superposition

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secondary structure, N to C, molecule

Ligands

Ligand code	Name	Ligand type
MSE	selenomethionine	modified residue

Structure information

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Unit cell parameters

Space Group: C 1 2 1
Unit Cell: a=83.11Å, b=23.19Å, c=105.62Å
α=90.00, β=107.48, γ=90.00
Solvent content: 47.75
Matthews coefficient: 2.35
Resolution range: 27.41-1.99Å (2.04-1.99Å)
R_all(%): 24.2
R_work(%): 24.0 (27.7)
R_free(%): 28.5 (32.8)
Num. observed reflections: 13431 (780)
Num. R_free reflections: 658 (41)
Completeness(%): 98.2 (79.5)
Num Atoms: 1454
Num Waters: 51
Num Hetatoms: 0
Model mean isotropic B factor (Å²): 24.040
RMSD bond length (Å): 0.016
RMSD bond angle: 1.535°
Filename uploaded: ct670pk_x1c2_final.pdb (uploaded on Oct 14, 2009 5:12 PM)
Inserted: Oct 14, 2009