Title: Structure-function analysis of lectin-like bacteriocins
Authors: Ghequire, Maarten ×
Garcia-Pino, Abel
Loris, Remy
De Mot, René #
Issue Date: 2011
Conference: International conference on Pseudomonas edition:13 location:Sydney date:4-7 September 2011
Abstract: Soil bacteria produce a plethora of antibacterial compounds that enable them to gain hold in nutrient-rich environments such as rhizospheres and spermospheres. The banana rhizosphere isolate Pseudomonas putida BW11M1 produces a lectin-like bacteriocin, denoted LlpA. In addition, two other LlpA-related antibacterial lectins were identified in the biocontrol strain Pseudomonas fluorescens Pf-5. Recently, two additional LlpA-like hypothetical proteins, identified by genome analysis of the phytopathogens Pseudomonas syringae and Xanthomonas citri, were produced recombinantly and shown to be functional bacteriocins.
So far, not much is known about this novel class of antibacterial proteins specifically targeting closely related bacteria. Our work focuses on the determination of the crystal structure of LlpA combined with the elucidation of its mode of action.

LlpA from strain BW11M1 was produced recombinantly in E. coli. The purified protein was crystallized and the structure determined. This revealed the presence of a tandem of two monocot mannose-binding lectin (MMBL) domains, followed by a C-terminal β-hairpin extension.
Soaking experiments of crystals with different carbohydrates showed that the C-terminal MMBL domain contains at least one active binding site that allows the binding of methyl-D-α-mannopyranoside. Point mutations in this lectin motif resulted in a significant drop of in vivo activity of LlpA. Another lectin motif in this domain may also contribute to the activity. The N-terminal domain adopts the same type of fold as the C-terminal domain but is structurally more divergent and appears not to contain a functional mannose-binding site.
Exchanging the N-terminal domain of LlpA with the homologous domains of the antibacterial lectins from strain Pf-5 and vice versa, still generated an active lectin, but resulted in a spectrum shift. Our results indicate that the N-terminal domain determines host specificity.
Publication status: published
KU Leuven publication type: IMa
Appears in Collections:Centre of Microbial and Plant Genetics
× corresponding author
# (joint) last author

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