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Structure of the HopA1(21-102)-ShcA chaperone-effector complex of Pseudomonas syringae reveals conservation of a virulence factor binding motif from animal to plant pathogens.

ABSTRACT: Pseudomonas syringae injects numerous bacterial proteins into host plant cells through a type 3 secretion system (T3SS). One of the first such bacterial effectors discovered, HopA1, is a protein that has unknown functions in the host cell but possesses close homologs that trigger the plant hypersensitive response in resistant strains. Like the virulence factors in many bacterial pathogens of animals, HopA1 depends upon a cognate chaperone in order to be effectively translocated by the P. syringae T3SS. Herein, we report the crystal structure of a complex of HopA1(21-102) with its chaperone, ShcA, determined to 1.56-Å resolution. The structure reveals that three key features of the chaperone-effector interactions found in animal pathogens are preserved in the Gram-negative pathogens of plants, namely, (i) the interaction of the chaperone with a nonglobular polypeptide of the effector, (ii) an interaction centered on the so-called ?-motif, and (iii) the presence of a conserved hydrophobic patch in the chaperone that recognizes the ?-motif. Structure-based mutagenesis and biochemical studies have established that the ?-motif is critical for the stability of this complex. Overall, these results show that the ?-motif interactions are broadly conserved in bacterial pathogens utilizing T3SSs, spanning an interkingdom host range.

SUBMITTER: Janjusevic R

PROVIDER: S-EPMC3562103 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Structure of the HopA1(21-102)-ShcA chaperone-effector complex of Pseudomonas syringae reveals conservation of a virulence factor binding motif from animal to plant pathogens.

Janjusevic Radmila R Quezada Cindy M CM Small Jennifer J Stebbins C Erec CE

Journal of bacteriology 20121130 4

Pseudomonas syringae injects numerous bacterial proteins into host plant cells through a type 3 secretion system (T3SS). One of the first such bacterial effectors discovered, HopA1, is a protein that has unknown functions in the host cell but possesses close homologs that trigger the plant hypersensitive response in resistant strains. Like the virulence factors in many bacterial pathogens of animals, HopA1 depends upon a cognate chaperone in order to be effectively translocated by the P. syringa ...[more]

PMID: 23204470

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Project description:Our previous work identified 23 low molecular weight (<3.5 kDa) crystallin peptides in the urea-soluble fractions of normal young, normal aged, and aged cataract human lenses. We found that one of these crystallin fragments, betaA3/A1(102-117) peptide (SDAYHIERLMSFRPIC), that are present in aged and cataract lens, increased the scattering of light by beta- and gamma-crystallins and alcohol dehydrogenase (ADH) and also reduced the chaperone-like activity of alphaB-crystallin. The present study was performed to identify the interacting sites of the betaA3/A1(102-117) peptide in alphaB-crystallin.betaA3/A1(102-117) peptide was first derivatized with sulfo-succinimidyl-2-[6-(biotinamido)-2-{p-azidobenzamido}-hexanoamido] ethyl-1-3 dithio propionate (sulfo-SBED), a photoactivable, heterotrifunctional biotin-containing cross-linker. The biotin-derivatized peptide was then incubated with alphaB-crystallin at 37 degrees C for 2 h to allow complex formation followed by photolysis to facilitate the transfer of the biotin label from the peptide to alphaB-crystallin. Label transfer was confirmed by western blot, and the labeled alphaB-crystallin was digested with trypsin. Tryptic peptides from alphaB-crystallin carrying the biotin label were purified by avidin affinity chromatography, and betaA3/A1(102-117) peptide interacting sites in alphaB-crystallin were identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and nanospray quadrupole time-of-flight mass spectrometry (QqTOF MS/MS).We found that the betaA3/A1(102-117) peptide interacted with alphaB-crystallin regions (70)LEKDR(74), (83)HFSPEELKVK(92), (91)VKVLGDVIEVHGK(103), (93)VLGDVIEVHGKHEER(107), and (121)KYR(123), which are part of the alpha-crystallin domain, and were previously shown to be part of the functional chaperone site in alphaB-crystallin. The betaA3/A1(102-117) peptide also interacted with regions at the COOH-terminal extension of alphaB-crystallin, (150)KQVSGPER(157), (164)EEKPAVTAAPK(174), and (164)EEKPAVTAAPKK(175). When two of the hydrophobic residues of betaA3/A1(102-117) peptide were replaced with hydrophilic residues, the resulting substituted peptide, SDADHGERLMSFRPIC, did not show the anti-chaperone property.This study confirmed the interactions between a low molecular weight peptide derived from betaA3/A1-crystallin found in aged and cataract lenses and alphaB-crystallin. The binding of betaA3/A1(102-117) peptide to the chaperone site and the COOH-terminal extension of alphaB-crystallin may explain its anti-chaperone property.

Dataset Information

Structure of the HopA1(21-102)-ShcA chaperone-effector complex of Pseudomonas syringae reveals conservation of a virulence factor binding motif from animal to plant pathogens.

Publications

Structure of the HopA1(21-102)-ShcA chaperone-effector complex of Pseudomonas syringae reveals conservation of a virulence factor binding motif from animal to plant pathogens.

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