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Extrusion of the C-terminal helix in navel orangeworm moth pheromone-binding protein (AtraPBP1) controls pheromone binding

Xu, W., Xu, X., Leal, W.S. and Ames, J.B. (2011) Extrusion of the C-terminal helix in navel orangeworm moth pheromone-binding protein (AtraPBP1) controls pheromone binding. Biochemical and Biophysical Research Communications, 404 (1). pp. 335-338.

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Link to Published Version: https://doi.org/10.1016/j.bbrc.2010.11.119
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Abstract

The navel orangeworm, Amyelois transitella (Walker), is an agricultural insect pest that can be controlled by disrupting male–female communication with sex pheromones, a technique known as mating disruption. Insect pheromone-binding proteins (PBPs) provide fast transport of hydrophobic pheromones through aqueous sensillar lymph and promote sensitive delivery of pheromones to receptors. Here we present a mutational analysis on a PBP from A. transitella (AtraPBP1) to evaluate how the C-terminal helix in this protein controls pheromone binding as a function of pH. Pheromone binds tightly to AtraPBP1 at neutral pH, but the binding is much weaker at pH below 5. Deletion of the entire C-terminal helix (residues 129–142) causes more than 100-fold increase in pheromone-binding affinity at pH 5 and only a 1.5-fold increase at pH 7. A similar pH-dependent increase in pheromone binding is also seen for the H80A/H95A double mutant that promotes extrusion of the C-terminal helix by disabling salt bridges at each end of the helix. The single mutants (H80A and H95A) also exhibit pheromone binding at pH below 5, but with ∼2-fold weaker affinity. NMR and circular dichroism data demonstrate a large overall structural change in each of these mutants at pH 4.5, indicating an extrusion of the C-terminal helix that profoundly affects the overall structure of the low pH form. Our results confirm that sequestration of the C-terminal helix at low pH as seen in the recent NMR structure may serve to block pheromone binding. We propose that extrusion of these C-terminal residues at neutral pH (or by the mutations in this study) exposes a hydrophobic cleft that promotes high affinity pheromone binding.

Item Type: Journal Article
Publisher: Academic Press
Copyright: © 2010 Elsevier Inc.
URI: http://researchrepository.murdoch.edu.au/id/eprint/37537
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