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Structural determinants for activity and specificity of the bacterial toxin LlpA.

Ghequire MG, Garcia-Pino A, Lebbe EK, Spaepen S, Loris R, De Mot R - PLoS Pathog. (2013)

Bottom Line: The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site.Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity.Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Centre of Microbial and Plant Genetics, University of Leuven, Heverlee-Leuven, Belgium.

ABSTRACT
Lectin-like bacteriotoxic proteins, identified in several plant-associated bacteria, are able to selectively kill closely related species, including several phytopathogens, such as Pseudomonas syringae and Xanthomonas species, but so far their mode of action remains unrevealed. The crystal structure of LlpABW, the prototype lectin-like bacteriocin from Pseudomonas putida, reveals an architecture of two monocot mannose-binding lectin (MMBL) domains and a C-terminal β-hairpin extension. The C-terminal MMBL domain (C-domain) adopts a fold very similar to MMBL domains from plant lectins and contains a binding site for mannose and oligomannosides. Mutational analysis indicates that an intact sugar-binding pocket in this domain is crucial for bactericidal activity. The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site. Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity. Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.

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Related in: MedlinePlus

Domain interactions within LlpABW.(A) The C-terminal hairpin extension (green cartoon) covers the interface between the N-domain (red surface representation) and the C-domain (blue surface representation). (B) Stereo view of the interactions between loop segments Val140-Asp145 (cyan) of the C-domain and Val115-Asp118 (yellow) and Ser31-Gln34 (orange) of the N-domain. Other structural elements are colored according to panel A. (C) Stereo view of the two-stranded β-sheet formed by strands β11a,b and β22a,b that links the N- and the C-domains and gives rise to domain swapping. Colors according to panel A and B.
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ppat-1003199-g002: Domain interactions within LlpABW.(A) The C-terminal hairpin extension (green cartoon) covers the interface between the N-domain (red surface representation) and the C-domain (blue surface representation). (B) Stereo view of the interactions between loop segments Val140-Asp145 (cyan) of the C-domain and Val115-Asp118 (yellow) and Ser31-Gln34 (orange) of the N-domain. Other structural elements are colored according to panel A. (C) Stereo view of the two-stranded β-sheet formed by strands β11a,b and β22a,b that links the N- and the C-domains and gives rise to domain swapping. Colors according to panel A and B.

Mentions: LlpABW is a very rigid molecule. The two monomers present in the asymmetric unit are essentially identical with a root-mean-square deviation (RMSD) of 0.34 Å for 270 Cα atoms. This RMSD value does not change significantly when the individual domains are fitted separately (0.32 Å for 120 Cα's of the N-domain and 0.22 Å for 115 Cα's of the C-domain), indicating that the inter-domain orientation is fixed. This stems from three sets of interactions (Figure 2). Both domains are connected by a two-stranded anti-parallel β-sheet that is involved in the β-strand swapping mentioned above and that links both domains. The C-terminal β-hairpin extension makes extensive contacts, through hydrophobic and hydrogen bonds, with both domains. Finally, the stretch Val140-Asp145 of the C-domain makes extensive contacts with stretch Val115-Asp118 and with the side chains of Ser15 and Pro32 of the N-domain.


Structural determinants for activity and specificity of the bacterial toxin LlpA.

Ghequire MG, Garcia-Pino A, Lebbe EK, Spaepen S, Loris R, De Mot R - PLoS Pathog. (2013)

Domain interactions within LlpABW.(A) The C-terminal hairpin extension (green cartoon) covers the interface between the N-domain (red surface representation) and the C-domain (blue surface representation). (B) Stereo view of the interactions between loop segments Val140-Asp145 (cyan) of the C-domain and Val115-Asp118 (yellow) and Ser31-Gln34 (orange) of the N-domain. Other structural elements are colored according to panel A. (C) Stereo view of the two-stranded β-sheet formed by strands β11a,b and β22a,b that links the N- and the C-domains and gives rise to domain swapping. Colors according to panel A and B.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585409&req=5

ppat-1003199-g002: Domain interactions within LlpABW.(A) The C-terminal hairpin extension (green cartoon) covers the interface between the N-domain (red surface representation) and the C-domain (blue surface representation). (B) Stereo view of the interactions between loop segments Val140-Asp145 (cyan) of the C-domain and Val115-Asp118 (yellow) and Ser31-Gln34 (orange) of the N-domain. Other structural elements are colored according to panel A. (C) Stereo view of the two-stranded β-sheet formed by strands β11a,b and β22a,b that links the N- and the C-domains and gives rise to domain swapping. Colors according to panel A and B.
Mentions: LlpABW is a very rigid molecule. The two monomers present in the asymmetric unit are essentially identical with a root-mean-square deviation (RMSD) of 0.34 Å for 270 Cα atoms. This RMSD value does not change significantly when the individual domains are fitted separately (0.32 Å for 120 Cα's of the N-domain and 0.22 Å for 115 Cα's of the C-domain), indicating that the inter-domain orientation is fixed. This stems from three sets of interactions (Figure 2). Both domains are connected by a two-stranded anti-parallel β-sheet that is involved in the β-strand swapping mentioned above and that links both domains. The C-terminal β-hairpin extension makes extensive contacts, through hydrophobic and hydrogen bonds, with both domains. Finally, the stretch Val140-Asp145 of the C-domain makes extensive contacts with stretch Val115-Asp118 and with the side chains of Ser15 and Pro32 of the N-domain.

Bottom Line: The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site.Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity.Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Centre of Microbial and Plant Genetics, University of Leuven, Heverlee-Leuven, Belgium.

ABSTRACT
Lectin-like bacteriotoxic proteins, identified in several plant-associated bacteria, are able to selectively kill closely related species, including several phytopathogens, such as Pseudomonas syringae and Xanthomonas species, but so far their mode of action remains unrevealed. The crystal structure of LlpABW, the prototype lectin-like bacteriocin from Pseudomonas putida, reveals an architecture of two monocot mannose-binding lectin (MMBL) domains and a C-terminal β-hairpin extension. The C-terminal MMBL domain (C-domain) adopts a fold very similar to MMBL domains from plant lectins and contains a binding site for mannose and oligomannosides. Mutational analysis indicates that an intact sugar-binding pocket in this domain is crucial for bactericidal activity. The N-terminal MMBL domain (N-domain) adopts the same fold but is structurally more divergent and lacks a functional mannose-binding site. Differential activity of engineered N/C-domain chimers derived from two LlpA homologues with different killing spectra, disclosed that the N-domain determines target specificity. Apparently this bacteriocin is assembled from two structurally similar domains that evolved separately towards dedicated functions in target recognition and bacteriotoxicity.

Show MeSH
Related in: MedlinePlus