Data collection statistics for native and selenomethionine substituted AmyR.

<p>Values in parentheses are for the highest resolution shell.</p

Ribbon representation of the overall structure of the AmyR monomer.

<p>The AmyR monomer is coloured by secondary structure. Secondary structure elements are labelled with residue numbers. The right panel is rotated 90°. β-strand 1 interacts with the equivalent residues in the dimer, shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0176049#pone.0176049.g002" target="_blank">Fig 2</a>.</p

Unmodelled density at crystal contact between molecules.

<p>(A) Electron density and difference map of the unmodelled density at the crystal contact. The main crystal contact forming density is central, while the two other chains are seen below. (B) An alternative view of the two chains.</p

Rotated views of the <i>E</i>. <i>amylovora</i> AmyR dimer.

<p>(A) Ribbon diagram, coloured by secondary structure. (B) Surface topography, coloured by surface charge at pH 7.4, red = negative, blue = positive.</p

Refinement statistics for native and selenomethionine substituted AmyR.

<p>Refinement statistics for native and selenomethionine substituted AmyR.</p

The water molecules between the dimer interface.

<p>Cross-section of the hydrophilic pocket at the dimer interface, showing the A and B chains coloured in gold and silver, with the highly ordered water molecules contained within.</p

Structural alignment of AmyR monomer with other YbjN and T3C proteins.

<p>The two views are rotated horizontally 90°. The alignment includes the PDB entries 1JYO:D (<i>Salmonella enterica</i> SicP, ice blue), 1S28:A (<i>Pseudomonas savastanoi</i> AvrPphF ORF1, gold), 1TTW:A (<i>Yersinia pestis</i> SycH, coral), 1XKP:B (<i>Yersinia pestis</i> SycN, grey), 2PLG:B (<i>Synechococcus elongates</i> T110839, pink), 3EPU:A (<i>Salmonella enterica</i> STM2138, sea green), 3KXY:J (<i>Escherichia coli</i> ExsC, brown), and 4H5B:A (<i>Deinococcus radiodurans</i> DR_1245, lilac), and 5FR7:A (<i>Erwinia amylovora</i> AmyR, yellow).</p

The crystal structure of <i>Erwinia amylovora</i> AmyR, a member of the YbjN protein family, shows similarity to type III secretion chaperones but suggests different cellular functions

<div><p>AmyR is a stress and virulence associated protein from the plant pathogenic Enterobacteriaceae species <i>Erwinia amylovora</i>, and is a functionally conserved ortholog of YbjN from <i>Escherichia coli</i>. The crystal structure of <i>E</i>. <i>amylovora</i> AmyR reveals a class I type III secretion chaperone-like fold, despite the lack of sequence similarity between these two classes of protein and lacking any evidence of a secretion-associated role. The results indicate that AmyR, and YbjN proteins in general, function through protein-protein interactions without any enzymatic action. The YbjN proteins of Enterobacteriaceae show remarkably low sequence similarity with other members of the YbjN protein family in Eubacteria, yet a high level of structural conservation is observed. Across the YbjN protein family sequence conservation is limited to residues stabilising the protein core and dimerization interface, while interacting regions are only conserved between closely related species. This study presents the first structure of a YbjN protein from Enterobacteriaceae, the most highly divergent and well-studied subgroup of YbjN proteins, and an in-depth sequence and structural analysis of this important but poorly understood protein family.</p></div

Location of conserved regions and residues of YbjN proteins superimposed on <i>E</i>. <i>amylovora</i> AmyR structure.

<p>(A) Sphere representation of AmyR displaying the two chains of the dimer in grey and green, with the atoms of conserved sidechains shown in red Van der Waals spheres. The main chains are partially transparent to show that the conserved residue side chains are mostly internalised or at the dimerization interface. (B) The same view as a ribbon diagram, with the YbjN protein conserved regions in red.</p

Sequence alignments of YbjN proteins.

<p>(A) Alignments of YbjN protein sequences from Enterobacteriaceae species, <i>Erwinia amylovora</i> (NCBI accession CBA20254); <i>Escherichia coli</i> (AJE55158); <i>Yersinia pestis</i> (ABP40742); <i>Salmonella enterica</i> (WP_000624814); <i>Shigella flexneri</i> (ABF03066); <i>Vibrio parahaemolyticus</i> (KKY40576)<i>; Serratia marcescens</i> (OKP20636); <i>Klebsiella pneumonia</i> (AHM80410); and Beta Proteobacteria <i>Ralstonia solanacearum</i> (WP_042591288). (B) Alignment of YbjN protein sequences from <i>Erwinia</i> species, <i>E</i>. <i>amylovora</i> (CBA20254); <i>E</i>. <i>pyrifoliae</i> (CAX56090); <i>E</i>. <i>piriflorinigrans</i> (WP_023654581); <i>E</i>. <i>tasmaniensis</i> (WP_012441893); <i>E</i>. <i>typographi</i> (WP_034891635); <i>E</i>. <i>iniecta</i> (WP_052896595); <i>E</i>. <i>billingiae</i> (WP_013201489); <i>E</i>. <i>mallotivora</i> (WP_034941268); <i>E</i>. <i>tracheiphila</i> (WP_016189698); <i>E</i>. <i>toletana</i> (WP_017802422); <i>E</i>. <i>oleae</i> (WP_034945603).</p