Biological Assembly 1  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 2-mer - A1B1 

Biological assembly 1 assigned by authors and generated by PQS (software)

Macromolecule Content

• Total Structure Weight: 37.58 kDa 
• Atom Count: 2674 
• Modelled Residue Count: 310 
• Deposited Residue Count: 348 
• Unique protein chains: 2

2CO7

Salmonella enterica SafA pilin in complex with the SafB chaperone (Type II)

• PDB DOI: 10.2210/pdb2CO7/pdb

• Classification: FIBRIL PROTEIN
• Organism(s): Salmonella enterica subsp. enterica serovar Typhimurium str. LT2
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2006-05-25 Released: 2006-06-27 
• Deposition Author(s): Remaut, H., Rose, R.J., Hannan, T.J., Hultgren, S.J., Radford, S.E., Ashcroft, A.E., Waksman, G.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 1.80 Å
• R-Value Free: 0.228 
• R-Value Work: 0.190 
• R-Value Observed: 0.192 

Literature

Donor-Strand Exchange in Chaperone-Assisted Pilus Assembly Proceeds Through a Concerted Beta-Strand Displacement Mechanism

Remaut, H., Rose, R.J., Hannan, T.J., Hultgren, S.J., Radford, S.E., Ashcroft, A.E., Waksman, G.

(2006) Mol Cell 22: 831

• PubMed: 16793551 
• DOI: 10.1016/j.molcel.2006.05.033
• Primary Citation of Related Structures:  
  2CNY, 2CNZ, 2CO1, 2CO2, 2CO3, 2CO4, 2CO6, 2CO7


• PubMed Abstract: 
  

Gram-negative pathogens commonly use the chaperone-usher pathway to assemble adhesive multisubunit fibers on their surface. In the periplasm, subunits are stabilized by a chaperone that donates a beta strand to complement the subunits' truncated immunoglobulin-like fold. Pilus assembly proceeds through a "donor-strand exchange" (DSE) mechanism whereby this complementary beta strand is replaced by the N-terminal extension (Nte) of an incoming pilus subunit. Using X-ray crystallography and real-time electrospray ionization mass spectrometry (ESI-MS), we demonstrate that DSE requires the formation of a transient ternary complex between the chaperone-subunit complex and the Nte of the next subunit to be assembled. The process is crucially dependent on an initiation site (the P5 pocket) needed to recruit the incoming Nte. The data also suggest a capping reaction displacing DSE toward product formation. These results support a zip-in-zip-out mechanism for DSE and a catalytic role for the usher, the molecular platform at which pili are assembled.

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Organizational Affiliation: 

Institute of Structural Molecular Biology at UCL/Birkbeck, Malet Street, London WC1E 7HX, United Kingdom; School of Crystallography, Malet Street, London WC1E 7HX, United Kingdom; Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom. Electronic address: [e-mail].

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
SAFA PILUS SUBUNIT	A	127	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2	Mutation(s): 0  Gene Names: safA, STM0299
UniProt
Find proteins for Q8ZRK4 (Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)) Explore Q8ZRK4  Go to UniProtKB:  Q8ZRK4

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
PUTATIVE FIMBRIAE ASSEMBLY CHAPERONE	B	221	Salmonella enterica subsp. enterica serovar Typhimurium str. LT2	Mutation(s): 0  Gene Names: safB, STM0300
UniProt
Find proteins for Q8ZRK3 (Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)) Explore Q8ZRK3  Go to UniProtKB:  Q8ZRK3

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
SO4	C [auth A], D [auth B]	SULFATE ION O4 S QAOWNCQODCNURD-UHFFFAOYSA-L

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 1.80 Å
• R-Value Free: 0.228 
• R-Value Work: 0.190 
• R-Value Observed: 0.192 
• Space Group: C 1 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 114.388	α = 90
b = 40.595	β = 95.82
c = 72.039	γ = 90

Software Package:

Software Name	Purpose
REFMAC	refinement
MOSFLM	data reduction
SCALA	data scaling
PHASER	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2006-05-25 
• Released Date: 2006-06-27 
Deposition Author(s): Remaut, H., Rose, R.J., Hannan, T.J., Hultgren, S.J., Radford, S.E., Ashcroft, A.E., Waksman, G.

Revision History  

• Version 1.0: 2006-06-27
  Type: Initial release
  
• Version 1.1: 2011-07-13
  Changes: Advisory, Version format compliance
• Version 1.2: 2019-10-09
  Changes: Data collection, Experimental preparation, Other