Structural determinants for activity and specificity of the bacterial toxin LlpA

PLoS Pathog. 2013 Feb;9(2):e1003199. doi: 10.1371/journal.ppat.1003199. Epub 2013 Feb 28.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry*
  • Anti-Bacterial Agents / metabolism
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Toxins / chemistry*
  • Bacterial Toxins / metabolism
  • Bacteriocins / chemistry*
  • Bacteriocins / metabolism
  • Bacteriocins / pharmacology
  • Circular Dichroism
  • Crystallization
  • DNA Mutational Analysis
  • DNA, Bacterial / analysis
  • DNA, Recombinant
  • Microbial Sensitivity Tests
  • Protein Binding
  • Protein Structure, Tertiary
  • Pseudomonas putida / genetics
  • Pseudomonas putida / metabolism*
  • Structure-Activity Relationship
  • Substrate Specificity


  • Anti-Bacterial Agents
  • Bacterial Toxins
  • Bacteriocins
  • DNA, Bacterial
  • DNA, Recombinant

Grants and funding

This work was financially supported by FWO Vlaanderen (Research project G.0393.09), by The Onderzoeksraad of the VUB, by VIB and by the Hercules Foundation. The authors acknowledge support of the European Community - Research Infrastructure Action under the FP6 “Structuring the European Research Area Program”, contract number: RII3-CT-2004-506008. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.