Activation of leukocyte movement and displacement of [3H]leukotriene B4 from leukocyte membrane preparations by (12R)- and (12S)-hydroxyeicosatetraenoic acid

Both (12R)- and (12S)-hydroxyeicosatetraenoic acid were demonstrated to produce aggregation of rat leukocytes and enhance human leukocyte chemokinesis. (12R)-Hydroxyeicosatetraenoic acid was 10-20-fold more potent than (12S)-hydroxyeicosatetraenoic acid but at least 500-fold less potent than leukotriene B4 in these assays. These relative potencies are correlated with the potencies of (12R)- and (12S)-hydroxyeicosatetraenoic acid for competition of [3H]leukotriene B4 binding to rat and human leukocyte membrane preparations.     

A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems

A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge.     

A phylogenomic approach to species delimitation in the mango fruit fly (Bactrocera frauenfeldi) complex: A new synonym of an important pest species with variable morphotypes (Diptera: Tephritidae)

Species that are dispersed across oceanic islands can have strong population structure due to genetic isolation, which makes it difficult to determine realistic and meaningful species boundaries. This becomes especially problematic when pest species are involved, and can result in undetected new invasions. The mango fruit fly, Bactrocera frauenfeldi (Schiner), is currently considered to be one of five morphologically similar members in a monophyletic species group distributed across Southeast Asia, Australasia, and Oceania, including three major pests. We used a phylogenomic approach with highly multiplexed amplicon sequencing to test species limits and evaluate the relationships among species in the B. frauenfeldi species complex and two closely related species. We obtained sequence data from 196 specimens for 395 nuclear DNA loci, totalling 102 kb, of which 2.2 kb were parsimony informative sites. Based on morphology, biogeography, and phylogenetic analyses, we conclude that there are five distinct species in the complex in our phylogeny. Our results show that the morphological differences between B. frauenfeldi and B. albistrigata (de Meijere) are part of a continuum that cannot be phylogenetically separated into monophyletic groups. We therefore synonymize the names of two major pests: B. albistrigata syn. rev. with B. frauenfeldi, making B. frauenfeldi now recognized as a widespread pest across Australasia and Southeast Asia. We evaluated the use of COI for pest recognition and conclude that it cannot reliably distinguish between six of the seven species we studied, thus new molecular approaches will be necessary for effective management and the prevention of incursions.     

Molecular mechanism of ligand recognition by membrane transport protein,Mhp1

The hydantoin transporter Mhp1 is a sodium‐coupled secondary active transport protein of the nucleobase‐cation‐symport family and a member of the widespread 5‐helix inverted repeat superfamily of transporters. The structure of Mhp1 was previously solved in three different conformations providing insight into the molecular basis of the alternating access mechanism. Here, we elucidate detailed events of substrate binding, through a combination of crystallography, molecular dynamics, site‐directed mutagenesis, biochemical/biophysical assays, and the design and synthesis of novel ligands. We show precisely where 5‐substituted hydantoin substrates bind in an extended configuration at the interface of the bundle and hash domains. They are recognised through hydrogen bonds to the hydantoin moiety and the complementarity of the 5‐substituent for a hydrophobic pocket in the protein. Furthermore, we describe a novel structure of an intermediate state of the protein with the external thin gate locked open by an inhibitor, 5‐(2‐naphthylmethyl)‐L‐hydantoin, which becomes a substrate when leucine 363 is changed to an alanine. We deduce the molecular events that underlie acquisition and transport of a ligand by Mhp1.     

Cation and sugar selectivity determinants in a novel family of transport proteins

A new family of homologous membrane proteins that transport galactosides–pentoses–hexuronides (GPH) is described. By analysing the aligned amino acid sequences of the GPH family, and by exploiting their different specificities for cations and sugars, we have designed mutations that yield novel insights into the nature of ligand binding sites in membrane proteins. Mutants have been isolated/constructed in the melibiose transport proteins of Escherichia coli Klebsiella pneumoniae and Salmonella typhimurium , and the lactose transport protein of Streptococcus thermophilus which facilitate uncoupled transport or have an altered cation and/or substrate specificity. Most of the mutations map in the amino-terminal region, in or near amphipathic α-helices II and IV, or in interhelix-loop 10–11 of the transport proteins. On the basis of the kinetic properties of these mutants, and the primary and secondary structure analyses presented here, we speculate on the cation binding pocket of this family of transporters. The regulation of the transporters through interaction with, or phosphorylation by, components of the phosphoenolpyruvate:sugar phosphotransferase system is also discussed.     

Aggregation of chlorophylls in monolayers.

The interaction of dioxane vapor with monolayer and multilayers of chlorophyll has been studied using electronic and infarared spectroscopies. Our results indicate the formation of a complex implying the oxygene of the dioxanc molecules with the magnesiums of adjacent chlorophyll molecules. These results are consistent with the molecular orbital calculations, using the "free electron network" method done by Le Brech, Leblanc and Antippa [Chem. Phys. Letters 26(1974) 37-44].     

Effect of membrane cholesterol on potassium transport in Mycoplasma mycoides var. Capri (PG3).

Relationships between membrane lipid composition and physiological properties, particularly intracellular potassium levels, have been studied at 37 degrees C in Mycoplasma mycoides var. Capri (PG3). Native organisms grown on medium supplemented with either oleic acid plus palmitic acid or elaidic acid have identical growth characteristics, acidification properties and intracellular K content. On the other hand, when the cholesterol normally present in the membrane (20--25% of total lipids) is reduced to less than 2%, we observe: (1) the intracellular K content decreases (20 microgram K/mg cell protein instead of 40) and is independent of the phase of growth; (2) K passive permeability is drastically increased but K distribution remains in equilibrium with the transmembrane potential (delta psi); (3) organisms stop growing at pH 6.5 (instead of 5.2) and acidification is reduced by 40%, suggesting a large increase in H+ permeability, and (4) intracellular Na contents rise from 3 to 9 microgram Na/mg cell protein. Replenishing cholesterol in membranes of depleted cells results in a recovery of the high intracellular K level (35--40 microgram K/mg cell protein) and acidification properties. It is suggested that cholesterol affects the cation content via the increase in proton permeability which in turn controls the value of the delta psi responsible for the value of intracellular K equilibrium. Changes in K passive permeability, although related to the amount of cholesterol present in the plasma membrane, are probably not involved in the control of the intracellular K level.