PDBsum entry 3fy3

Toxin

PDB id: 3fy3

Contents

Protein chain

234 a.a. *

* Residue conservation analysis

PDB id:

3fy3

Name:

Toxin

Title:

Crystal structure of truncated hemolysin a from p. Mirabilis

Structure:

Hemolysin. Chain: a. Fragment: unp residues 30-265. Engineered: yes

Source:

Proteus mirabilis. Organism_taxid: 584. Gene: hpma. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.80Å R-factor: 0.151 R-free: 0.203

Authors:

T.M.Weaver,J.R.Thompson,L.J.Bailey,G.T.Wawrzyn,J.M.Hocking,D.R.Howard

Key ref:

T.M.Weaver et al. (2009). Structural and functional studies of truncated hemolysin A from Proteus mirabilis. J Biol Chem, 284, 22297-22309. PubMed id: 19494116 DOI: 10.1074/jbc.M109.014431

Date:

21-Jan-09 Release date: 02-Jun-09

Protein chain

P16466  (HLYA_PROMI) -  Hemolysin from Proteus mirabilis

Seq: 1577 a.a.

Struc: 234 a.a.

DOI no: 10.1074/jbc.M109.014431

J Biol Chem 284:22297-22309 (2009)

PubMed id: 19494116

Structural and functional studies of truncated hemolysin A from Proteus mirabilis.

T.M.Weaver, J.M.Hocking, L.J.Bailey, G.T.Wawrzyn, D.R.Howard, L.A.Sikkink, M.Ramirez-Alvarado, J.R.Thompson.

ABSTRACT

In this study we analyzed the structure and function of a truncated form of hemolysin A (HpmA265) from Proteus mirabilis using a series of functional and structural studies. Hemolysin A belongs to the two-partner secretion pathway. The two-partner secretion pathway has been identified as the most common protein secretion pathway among Gram-negative bacteria. Currently, the mechanism of action for the two-partner hemolysin members is not fully understood. In this study, hemolysis experiments revealed a unidirectional, cooperative, biphasic activity profile after full-length, inactive hemolysin A was seeded with truncated hemolysin A. We also solved the first x-ray structure of a TpsA hemolysin. The truncated hemolysin A formed a right-handed parallel beta-helix with three adjoining segments of anti-parallel beta-sheet. A CXXC disulfide bond, four buried solvent molecules, and a carboxyamide ladder were all located at the third complete beta-helix coil. Replacement of the CXXC motif led to decreased activity and stability according to hemolysis and CD studies. Furthermore, the crystal structure revealed a sterically compatible, dry dimeric interface formed via anti-parallel beta-sheet interactions between neighboring beta-helix monomers. Laser scanning confocal microscopy further supported the unidirectional interconversion of full-length hemolysin A. From these results, a model has been proposed, where cooperative, beta-strand interactions between HpmA265 and neighboring full-length hemolysin A molecules, facilitated in part by the highly conserved CXXC pattern, account for the template-assisted hemolysis.

Selected figure(s)

Figure 2.
The crystal structures of HpmA265, Fha30, and HMW1-PP show differences within the top and flanking anti-parallel β-sheet regions.a, the Cα coordinates have been superimposed between HpmA265 and Fha30. The trace for HpmA Cα atoms has been colored black in both images. Structural differences between HpmA265 and Fha30 have been colored cyan for the top and flanking regions apβ1, apβ2, and apβ3, while differences within β-arc regions have been colored red. The largest structural differences between HpmA265 and Fha30 lie at the flanking anti-parallel sheet apβ3. This shift accommodates a 12-residue insertion between β22 and β23 in HpmA265 and preserves the integrity of the β-helix core alignment. b, structural differences between HpmA265 and HMW1-PP have been colored cyan for anti-parallel regions, magenta for α-helix regions, and red for β-arcs. The large shift at the N-terminal end derives from a global superposition of three anti-parallel strands within HMW1-PP onto the four anti-parallel strands within HpmA265. This large difference stems from moving β2 of HMW1-PP between β1 and β2 of HpmA265. The N-terminal superposition also leaves β5 and β6 of HpmA265 without matching HMW1-PP strands. Additionally, HMW1-PP has an α-helix in place of two of the anti-parallel strands within apβ3. This creates another location of large structural difference. In both instances, the structural agreement between β-helix core Cα atoms is well maintained, especially within the NPNG motif (colored green).

Figure 9.
HpmA265 crystallographic dry dimer interface leading to a filamentous appearance.a, the HpmA265 dry dimer forms a filamentous structure. The solid lines represent hydrogen bonds shared between β23 strands of both subunits. b, the dry dimer interface has been displayed where β23 from each monomer has been colored independently. The anti-parallel interstrand hydrogen-bonding network creates dry, sterically compatible dimer interface. Dashed lines represent hydrogen bonds, while van der Waal's surfaces have been provided for various hydrophobic side chains.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2009, 284, 22297-22309) copyright 2009.

Figures were selected by an automated process.