PDBsum entry 2co7

Fibril protein

PDB id: 2co7

Contents

Protein chains

112 a.a.

198 a.a. *

Ligands

SO4 ×2

Waters ×274

* Residue conservation analysis

PDB id:

2co7

Name:

Fibril protein

Title:

Salmonella enterica safa pilin in complex with the safb chaperone (type ii)

Structure:

Safa pilus subunit. Chain: a. Fragment: core pilin domain, nte deleted, residues 46-170. Engineered: yes. Mutation: yes. Putative fimbriae assembly chaperone. Chain: b. Synonym: safb chaperone. Engineered: yes

Source:

Salmonella typhimurium. Organism_taxid: 99287. Strain: lt2. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

1.80Å R-factor: 0.192 R-free: 0.228

Authors:

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

Key ref:

H.Remaut et al. (2006). Donor-strand exchange in chaperone-assisted pilus assembly proceeds through a concerted beta strand displacement mechanism. Mol Cell, 22, 831-842. PubMed id: 16793551 DOI: 10.1016/j.molcel.2006.05.033

Date:

25-May-06 Release date: 27-Jun-06

Protein chain

Q8ZRK4  (Q8ZRK4_SALTY) -  Outer membrane protein from Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)

Seq: 170 a.a.

Struc: 112 a.a.

Protein chain

Q8ZRK3  (Q8ZRK3_SALTY) -  Fimbriae assembly chaparone from Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720)

Seq: 237 a.a.

Struc: 198 a.a.

DOI no: 10.1016/j.molcel.2006.05.033

Mol Cell 22:831-842 (2006)

PubMed id: 16793551

Donor-strand exchange in chaperone-assisted pilus assembly proceeds through a concerted beta strand displacement mechanism.

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

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.

Selected figure(s)

Figure 4.
Figure 4. Kinetics of DSE
ESI-MS data showing (A) the decline of the initial SafB-SafA[Ntd2] complex, (B) the appearance of the SafA[Ntd2]-A[Nte] product, (C) the release of free SafB, and (D) the decline in concentration of the ternary SafB-SafA[Ntd2]-A[Nte] complex. Either wt A[Nte] (dark blue) or different variant peptides (F17A, green; I15A, light blue; V13A, orange; or F3A, magenta) were used to initiate the reaction. A control experiment in which no peptide was added is shown in (A) as a red dotted line. See the Supplemental Data for normalization procedure.

Figure 7.
Figure 7. Model for the Mechanism of DSE In Vitro and In Vivo
(A) Schematic representation of DSE in vitro. Chaperone and subunit are labeled (i) and (ii), respectively. In the chaperone, strands G[1] and F[1] are represented as solid black lines. In the subunit, strand F, which directly interacts with the G[1] donor strand, is depicted in blue. An incoming Nte (depicted in red) forms a ternary complex with the chaperone-subunit complex at the P5 pocket (indicated by a thicker line). DSE then proceeds and terminates by dissociation of the chaperone-subunit complex and insertion of the P^* residue in the P^* pocket.
(B) Schematic representation of a single incorporation cycle at the usher (see text). Chaperone and usher are colored gray and light blue, respectively. For clarity, subunits are differentiated by color (yellow, red, green, orange, and blue), with the last incorporated subunit in orange and the incoming subunit in blue. The N-terminal and C-terminal domains of the usher are indicated.

The above figures are reprinted by permission from Cell Press: Mol Cell (2006, 22, 831-842) copyright 2006.

Figures were selected by an automated process.