Franchises lost and gained: post-coloniality and the development of women’s rights in Canada

The Canadian constitution is to some extent characterised by its focus on equality, and in particular gender equality. This development of women’s rights in Canada and the greater engagement of women as political actors is often presented as a steady linear process, moving forwards from post-enlightenment modernity. This article seeks to disturb this ‘discourse of the continuous,’ by using an analysis of the pre-confederation history of suffrage in Canada to both refute a simplistic linear view of women’s rights development and to argue for recognition of the Indigenous contribution to the history of women’s rights in Canada. The gain of franchise and suffrage movements in Canada in the late nineteenth and early twentieth century are, rightly, the focus of considerable study (Pauker 2015), This article takes an alternative perspective. Instead, it examines the exercise of earlier franchises in pre-confederation Canada. In particular it analyses why franchise was exercised more widely in Lower Canada and relates this to the context of the removal of franchises from women prior to confederation

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Systematic mutational analysis of the putative hydrolase PqsE: toward a deeper molecular understanding of virulence acquisition in Pseudomonas aeruginosa.

International audiencePseudomonas aeruginosa is an important opportunistic human pathogen that can establish bacterial communication by synchronizing the behavior of individual cells in a molecular phenomenon known as "quorum sensing". Through an elusive mechanism involving gene products of the pqs operon, the PqsE enzyme is absolutely required for the synthesis of extracellular phenazines, including the toxic blue pigment pyocyanin, effectively allowing cells to achieve full-fledged virulence. Despite several functional and structural attempts at deciphering the role of this relevant enzymatic drug target, no molecular function has yet been ascribed to PqsE. In the present study, we report a series of alanine scanning experiments aimed at altering the biological function of PqsE, allowing us to uncover key amino acid positions involved in the molecular function of this enzyme. We use sequence analysis and structural overlays with members of homologous folds to pinpoint critical positions located in the vicinity of the ligand binding cleft and surrounding environment, revealing the importance of a unique C-terminal α-helical motif in the molecular function of PqsE. Our results suggest that the active site of the enzyme involves residues that extend further into the hydrophobic core of the protein, advocating for a lid-like movement of the two terminal helices. This information should help design virtual libraries of PqsE inhibitors, providing means to counter P. aeruginosa virulence acquisition and helping to reduce nosocomial infections

Residues delineating the tunnel-shaped active site of PqsE.

<p>A–B) Access to the active site of PqsE is restricted by a very narrow and elongated tunnel-shaped cavity displayed in cyan. The solvent accessible surface was computed with CAVER <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073727#pone.0073727-Gilis1" target="_blank">[35]</a> and the co-crystalized benzoate moiety (BZ) is shown in green ball-and-stick representation (PDB entry 2Q0I). Residue side chains are labeled, displayed in ball-and-stick representation, and colored according to their impact on pyocyanin production upon mutation (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073727#pone-0073727-g006" target="_blank">Figure 6</a>). C) The benzoate molecule is displayed from the S285 tunnel entrance in WT PqsE and shows clear solvent accessibility to the active site. D) The modeled S285W replacement shows the blocked entrance of the tunnel caused by the indole side chain of tryptophan. E) The benzoate molecule is displayed from the Q272 tunnel entrance in WT PqsE. F) The modeled Q272A replacement shows a modest yet significant tunnel enlargement. Amino acid replacements were generated using the PyMOL mutation function.</p

Alanine scanning of critically positioned residues in PqsE.

<p>A–B) Sixteen residues were selected based on their potential role (s) in ligand stabilization, discrimination and/or catalytic function in the vicinity of the active site cavity. C–D) Six residues were targeted in the C-terminal α8/α9 motif unique to PqsE. E–F) Five residues were selected to verify the potential importance of the KH-like motif in substrate recognition and/or stabilization. Residue side chains are labeled, displayed in ball-and-stick representation, and colored according to their impact on pyocyanin production upon mutation (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073727#pone-0073727-g006" target="_blank">Figure 6</a>). The two catalytic iron atoms are depicted as yellow spheres.</p

Identification of a KH-like binding motif near the active site of PqsE.

<p>KH domains are eukaryotic and prokaryotic protein motifs involved in RNA and/or ssDNA recognition found in proteins associated with transcriptional and translational regulation. A) The type I KH3 domain of hnRNP K is shown in complex with a ssDNA 10mer (PDB entry 1J5K). The positively charged residues of the KH signature (K22, K31, R40) are labeled and shown in ball-and-stick representation. B–C) Overlay of the KH3 domain of hnRNP K with the KH-like kinked helix-loop-helix motif of PqsE. Side chains of positively charged residues in the KH-like motif are labeled and displayed in ball-and-stick representation. The color code corresponds to the impact of a mutation on pyocyanin production in <i>P. aeruginosa</i> (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073727#pone-0073727-g006" target="_blank">Figure 6</a>). The side chain of D130, which was mutated to disrupt the possible salt bridge it forms with K101, is also displayed. The two conserved active-site iron (Fe) atoms in PqsE are depicted as yellow spheres.</p

Structural overlays of PqsE homologues adopting the metallo-β-lactamase fold.

<p>A) Conserved active-site localization for eight proteins adopting the metallo-β-lactamase fold (PDB entries 1MQO, 1ZNB, 1JJT, 1KO3, 1X8H, 2YZ3, 1ZTC, and 1QH5). The two conserved active-site metal atoms are depicted as yellow spheres. B) Solvent accessible active-site cavity for a typical member of the metallo-β-lactamase fold (PDB entry 1MQO). The solvent accessible cavity was computed with CAVER <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073727#pone.0073727-Gilis1" target="_blank">[35]</a> and is depicted as a gray surface. C) The α8 and α9 helices (in pink) restrict ligand access to the active site of PqsE by forming a narrow and elongated tunnel. The solvent accessible surface tunnel was computed with CAVER and is shown in cyan (PDB entry 2Q0I). D) Superposition of PqsE (gray) and the structural homologue ST1585 from <i>Sulfolobus tokodaii</i> (blue). ST1585 is the only structurally resolved homologue with such high similarity in the protein core (Cα RMSD of 2.8 Å) and a similar α-helical motif restricting active-site access by forming a narrow tunnel-shaped entrance (cyan surface).</p

Pyocyanin production of a <i>P. aeruginosa</i> PA14 <i>pqsE⁻</i> strain transformed with WT PqsE and 28 mutational variants of PqsE.

<p>PqsE variants were generated by introducing 17 mutations in the putative active site, 6 in the additional C-terminal α8/α9 motif and 5 in the KH-like motif. Pyocyanin production (mg/L) is drastically affected for 12 PqsE variants (red, less than 10% pyocyanin production relative to WT complementation), confirming the critical role of these residues in enzyme activity and/or stability. Five low-producing variants (magenta, less than 50% pyocyanin production relative to WT complementation) still play important roles in the function of this enzyme, while 11 gray variants show no significant pyocyanin production variation relative to WT (blue).</p

Pyocyanin complementation of a <i>P. aeruginosa</i> PA14 <i>pqsE⁻</i> strain transformed with the PqsE variants and the predicted free energy variation caused by each point mutation.

a<p>Pyocyanin production (mg/L) was measured in triplicate as described in the experimental procedures. The mean value (± standard deviation) is shown. <i>^b</i> Free energy variations caused by point mutants of PqsE, as predicted by the PoPMuSiC software (v.2). <i>^c</i> Calculated solvent accessibility for each WT residue, ranging from 0 (fully buried in the protein core) to 1 (fully accessible to the solvent).</p