Male and female brain evolution is subject to contrasting selection pressures in primates

The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the "social brain" hypothesis) is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20) add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative) is related most closely to neocortex volume, but male sociality (which is more competitive and combative) is more closely related to subcortical units (notably those associated with emotional responses). Thus different brain units have responded to different selection pressures.     

Effect of sex and bright coloration on survival and predator‐induced wing damage in an aposematic lantern fly with startle display

1. Aposematic coloration in prey promotes its survival by conspicuously advertising unpalatability to predators. Although classical examples of aposematic signals involve constant presentation of a signal at a distance, some animals suddenly display warning colours only when they are attacked. 2. Characteristics of body parts suddenly displayed, such as conspicuous coloration or eyespot pattern, may increase the survival of the prey by startling the predator, and/or by signalling unpalatability to the predators at the moment of attack. 3. The adaptive value of such colour patterns suddenly displayed by unpalatable prey has not been studied. We experimentally blackened the red patch in the conspicuous red–white–black hindwing pattern displayed by an unpalatable insect Lycorma delicatula White (Hemiptera: Fulgoridae) in response to predator's attack. 4. There was no evidence that the presence of the red patch increased prey survival over several weeks. We hypothesise that predators generalised from the red–white–black patches on the hindwings of unpalatable L. delicatula to any similar wing display as a signal of unpalatability. Because a higher proportion of males than females stay put at their resting sites, displaying their wings in response to repeated attacks by predators, wing damage was more frequent in males than in females. 5. To our knowledge, this is the first experimental test of an adaptive role of aposematic signals presented by unpalatable prey during sudden displays triggered by direct predatory attack.     

Rapid ex vivo expansion of highly enriched human invariant natural killer T cells via single antigenic stimulation for cell therapy to prevent graft-versus-host disease

Background aims

CD1d-restricted invariant natural killer (iNK) T cells are rare regulatory T cells that may contribute to the immune-regulation in allogeneic stem cell transplantation (ASCT). Here, we sought to develop an effective strategy to expand human iNK T cells for use in cell therapy to prevent graft-versus-host disease (GVHD) in ASCT.

Mechanisms of Allosteric Activation and Inhibition of the Deoxyribonucleoside Triphosphate Triphosphohydrolase from Enterococcus faecalis

EF1143 from Enterococcus faecalis, a life-threatening pathogen that is resistant to common antibiotics, is a homo-tetrameric deoxyribonucleoside triphosphate (dNTP) triphosphohydrolase (dNTPase), converting dNTPs into the deoxyribonucleosides and triphosphate. The dNTPase activity of EF1143 is regulated by canonical dNTPs, which simultaneously act as substrates and activity modulators. Previous crystal structures of apo-EF1143 and the protein bound to both dGTP and dATP suggested allosteric regulation of its enzymatic activity by dGTP binding at four identical allosteric sites. However, whether and how other canonical dNTPs regulate the enzyme activity was not defined. Here, we present the crystal structure of EF1143 in complex with dGTP and dTTP. The new structure reveals that the tetrameric EF1143 contains four additional secondary allosteric sites adjacent to the previously identified dGTP-binding primary regulatory sites. Structural and enzyme kinetic studies indicate that dGTP binding to the first allosteric site, with nanomolar affinity, is a prerequisite for substrate docking and hydrolysis. Then, the presence of a particular dNTP in the second site either enhances or inhibits the dNTPase activity of EF1143. Our results provide the first mechanistic insight into dNTP-mediated regulation of dNTPase activity.     

Association between polymorphisms of eNOS and GPx-1 genes, activity of free-radical processes and in-stent restenosis

Our aim was to examine correlations between polymorphisms in five antioxidant enzymes genes, activity of free-radical processes, and the risk of restenosis after coronary artery stenting with bare metal stents (BMS). A total of 101 male patients who underwent intracoronary stenting using BMS and coronary angiography follow-up of 6 months were enrolled in: group with in-stent restenosis (n = 44) and without restenosis (n = 57). The content of lipoperoxides and malondialdehyde (MDA) in Low-density lipoprotein (LDL), activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) in erythrocytes, and genotypes polymorphisms of the CAT gene (?262C/T), paraoxonase-1 (PON-1) gene (163T/A and 575A/G), endothelial nitric oxide synthase (eNOS) gene (298G/T (rs#1799983) and ?786T/C), GPx-1 gene (599C/T (rs#1050450)), and glutathione-S-transferase (GSTP) gene (313A/G) were determined. In carriers of the minor allele of 599C/T polymorphism of the GPx-1 gene, activity of GPx in erythrocytes was lower by 17 % than in wild allele homozygotes, while the content of lipoperoxides in LDL was higher by 74 %. T-allele of 599C/T polymorphism of the GPx-1 gene (OR = 2.9; 95 % CI: 1.23–6.82) and T-allele of 298G/T polymorphism of the eNOS gene (OR = 2.79; 95 % CI: 1.17–6.66) were associated with the risk of in-stent restenosis. Minor alleles of polymorphisms 298G/T of the eNOS gene and 599C/T of the GPx-1 gene are associated with an increased risk of in-stent restenosis. Minor allele of the GPx-1 gene 599C/T polymorphism leads to a decrease of the GPx activity and increase of the activity of free-radical processes.     

Analysis of the functional coupling between calmodulin's calcium binding and peptide recognition properties

The enhancement of calmodulin's (CaM) calcium binding activity by an enzyme or a recognition site peptide and its diminution by key point mutations at the protein recognition interface (e.g., E84K-CaM), which is more than 20 A away from the nearest calcium ligation structure, can be described by an expanded version of the Adair-Klotz equation for multiligand binding. The expanded equation can accurately describe the calcium binding events and their variable linkage to protein recognition events can be extended to other CaM-regulated enzymes and can potentially be applied to a diverse array of ligand binding systems with allosteric regulation of ligand binding, whether by other ligands or protein interaction. The 1.9 A resolution X-ray crystallographic structure of the complex between E84K-CaM and RS20 peptide, the CaM recognition site peptide from vertebrate smooth muscle and nonmuscle forms of myosin light chain kinase, provides insight into the structural basis of the functional communication between CaM's calcium ligation structures and protein recognition surfaces. The structure reveals that the complex adapts to the effect of the functional mutation by discrete adjustments in the helix that contains E84. This helix is on the amino-terminal side of the helix-loop-helix structural motif that is the first to be occupied in CaM's calcium binding mechanism. The results reported here are consistent with a sequential and cooperative model of CaM's calcium binding activity in which the two globular and flexible central helix domains are functionally linked, and provide insight into how CaM's calcium binding activity and peptide recognition properties are functionally coupled.     

Cryopreservation of red raspberry cultivars from the VIR <Emphasis Type="Italic">in vitro</Emphasis> collection using a modified droplet vitrification method

The goal of the present study was to analyze the post-cryogenic recovery of 12 red raspberry cultivars from the N.I. Vavilov All-Russian Institute of Plant Genetic Resources in vitro collection. The 1.1–1.8 mm shoot tips of microplants were subjected to cryopreservation using the modified droplet vitrification method. The current modifications to the droplet vitrification protocol included the elimination of the initial pretreatment stage of the microplants, and the use of modified media at the stages of initial micropropagation, explant isolation, and post-cryogenic regeneration. The optimized method reduced the duration of some cryopreservation stages compared to the initial protocol, and reduced the total procedure from 14 to 11 wk. This modified cryopreservation method also demonstrated a relatively high level of post-cryogenic regeneration. Depending on the genotype, the shoot recovery of explants after rewarming varied from 24.2–89.3% and averaged 58.8 ± 5.3%. There was a statistically significant influence of the genotype on the shoot recovery after rewarming. No differences in inter simple sequence repeats and in start codon targeted marker spectra were found between post-cryopreservation microplants and donor in vitro plants from two red raspberry cultivars.     

Crystal Structures of YkuI and Its Complex with Second Messenger Cyclic Di-GMP Suggest Catalytic Mechanism of Phosphodiester Bond Cleavage by EAL Domains

Cyclic di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger that is involved in the regulation of cell surface-associated traits and the persistence of infections. Omnipresent GGDEF and EAL domains, which occur in various combinations with regulatory domains, catalyze c-di-GMP synthesis and degradation, respectively. The crystal structure of full-length YkuI from Bacillus subtilis, composed of an EAL domain and a C-terminal PAS-like domain, has been determined in its native form and in complex with c-di-GMP and Ca²⁺. The EAL domain exhibits a triose-phosphate isomerase-barrel fold with one antiparallel β-strand. The complex with c-di-GMP-Ca²⁺ defines the active site of the putative phosphodiesterase located at the C-terminal end of the β-barrel. The EAL motif is part of the active site with Glu-33 of the motif being involved in cation coordination. The structure of the complex allows the proposal of a phosphodiesterase mechanism, in which the divalent cation and the general base Glu-209 activate a catalytic water molecule for nucleophilic in-line attack on the phosphorus. The C-terminal domain closely resembles the PAS-fold. Its pocket-like structure could accommodate a yet unknown ligand. YkuI forms a tight dimer via EAL-EAL and trans EAL-PAS-like domain association. The possible regulatory significance of the EAL-EAL interface and a mechanism for signal transduction between sensory and catalytic domains of c-di-GMP-specific phosphodiesterases are discussed.The dinucleotide cyclic di-GMP (c-di-GMP) was discovered about 20 years ago when it was found to regulate the activity of cellulase synthase in Acetobacter xylinum (1). However, its prominent role as a global second messenger has been realized only upon the recent recognition of the omnipresence of genes coding for domains that catalyze c-di-GMP biosynthesis and degradation in eubacteria (2). GGDEF domains catalyze the condensation of two GTP molecules to the cyclic 2-fold symmetric dinucleotide (diguanylate cyclase activity (3-6)), whereas EAL domains are involved in its degradation to yield the linear dinucleotide pGpG (phosphodiesterase (PDE)⁴ A activity) (3, 7-9). Recently, also HD-GYP domains have been implicated in c-di-GMP-specific PDE activity (10). All the domains have been named according to their sequence signature motifs. They are typically found in combinations with various other, mostly sensory or regulatory, domains. It is thought that the balance between antagonistic diguanylate cyclase and PDE-A activities determines the cellular level of c-di-GMP and, thus, affects a variety of physiological processes in bacteria.It has been shown that, in general, c-di-GMP regulates cell surface-associated traits and community behavior such as biofilm formation (for reviews see Refs. 11-12), and its relevance to the virulence of pathogenic bacteria has been demonstrated (11, 13, 14). In particular, the dinucleotide has been proposed to orchestrate the switch between acute and persistent phase of infection.The best characterized diguanylate cyclase is PleD from Caulobacter crescentus with a Rec-Rec-GGDEF domain architecture (Rec indicates response regulator receiver domain). The structure of its GGDEF domain revealed a single GTP-binding site and suggested that dimerization is the prerequisite for enzymatic activity (4). This has been corroborated recently by crystallography showing directly that modification of the first Rec domain, mimicking phosphorylation by the cognate kinase, induces formation of a tightly packed dimer (15). Additionally, an upper limit of c-di-GMP levels in the cell seems to be ensured by potent allosteric product inhibition of the PleD cyclase (4, 15, 16). Recently, the crystal structure of another diguanylate cyclase, WspR from Pseudomonas aeruginosa with a Rec-GGDEF domain architecture, has been determined (17), which showed a tetrameric quaternary structure and active and feedback inhibition sites that are very similar to those in PleD.For EAL domains, it has been demonstrated that genetic knock-out results in phenotypes that are in line with the paradigm that an elevated cellular c-di-GMP concentration corresponds to a sessile and a low concentration to a motile bacterial life style (13, 18, 19). Only recently, EAL-mediated PDE-A activity has been measured in vitro (7-9, 20-22).The Bacillus subtilis YkuI protein was targeted for structure determination by the Midwest Center for Structural Genomics as a member of the large sequence family that contains EAL (Pfam number PF00563) domains. Here we report the crystal structure of YkuI showing the fold of the N-terminal EAL domain and the C-terminal PAS-like domain. Co-crystallization with c-di-GMP revealed the substrate binding mode and allows the proposal of a catalytic mechanism. The PAS-like domain most probably has regulatory function, which is discussed. Recently, another EAL structure has been deposited in the Protein Data Bank by the Midwest Center for Structural Genomics, the EAL domain of a GGDEF-EAL protein from Thiobacillus denitrificans (tdEAL; PDB code 2r6o). Comparison of the two structures suggests a possible regulatory mechanism.     

Structure of the Type III Secretion Effector Protein ExoU in Complex with Its Chaperone SpcU

Disease causing bacteria often manipulate host cells in a way that facilitates the infectious process. Many pathogenic gram-negative bacteria accomplish this by using type III secretion systems. In these complex secretion pathways, bacterial chaperones direct effector proteins to a needle-like secretion apparatus, which then delivers the effector protein into the host cell cytosol. The effector protein ExoU and its chaperone SpcU are components of the Pseudomonas aeruginosa type III secretion system. Secretion of ExoU has been associated with more severe infections in both humans and animal models. Here we describe the 1.92 Å X-ray structure of the ExoU–SpcU complex, a full-length type III effector in complex with its full-length cognate chaperone. Our crystallographic data allow a better understanding of the mechanism by which ExoU kills host cells and provides a foundation for future studies aimed at designing inhibitors of this potent toxin.