Identification of novel bifunctional calmodulin-binding and microtubule-stabilizing motifs in STOP proteins.

Although microtubules are intrinsically labile tubulin assemblies, many cell types contain stable polymers, resisting depolymerizing conditions such as exposure to the cold or the drug nocodazole. This microtubule stabilization is largely due to polymer association with STOP proteins. There are several STOP variants, some with capacity to induce microtubule resistance to both the cold and nocodazole, others with microtubule cold stabilizing activity only. These microtubule-stabilizing effects of STOP proteins are inhibited by calmodulin and we now demonstrate that they are determined by two distinct kinds of repeated modular sequences (Mn and Mc), both containing a calmodulin-binding peptide, but displaying different microtubule stabilizing activities. Mn modules induce microtubule resistance to both the cold and nocodazole when expressed in cells. Mc modules, which correspond to the STOP central repeats, have microtubule cold stabilizing activity only. Mouse neuronal STOPs, which induce both cold and drug resistance in cellular microtubules, contain three Mn modules and four Mc modules. Compared with neuronal STOPs, the non-neuronal F-STOP lacks multiple Mn modules and this corresponds with an inability to induce nocodazole resistance. STOP modules represent novel bifunctional calmodulin-binding and microtubule-stabilizing sequences that may be essential for the generation of the different patterns of microtubule stabilization observed in cells.     

A rebuttal to a recent article by González and Pabón-Mora (2017) claiming the absence of polycotyly and the presence of endosperm in <Emphasis Type="Italic">Psittacanthus</Emphasis> (Loranthaceae)

The claim by González & Pabón-Moran (Brittonia 69: 176–185, 2017) that Psittacanthus (Loranthaceae) lacks polycotyly but has endosperm is shown to be based both on taxonomic misidentification and misinterpretation of seedling structure. The absence of endosperm and the presence of polycotyly in some species has been abundantly confirmed in the literature, much of the contents of which is ignored by González & Pabón-Moran.     

Efficient secretory production of large-size heterologous enzymes in Bacillus subtilis: A secretory partner and directed evolution

Secretory production of recombinant proteins provides a simple approach to the production and purification of target proteins in the enzyme industry. We developed a combined strategy for the secretory production of three large-size heterologous enzymes with a special focus on 83-kDa isoamylase (IA) from an archaeon Sulfolobus tokodaii in a bacterium Bacillus subtilis. First, a secretory protein of the B. subtilis family 5 glycoside hydrolase endoglucanase (Cel5) was used as a fusion partner, along with the NprB signal peptide, to facilitate secretory production of IA. This secretory partner strategy was effective for the secretion of two other large enzymes: family 9 glycoside hydrolase from Clostridium phytofermentas and cellodextrin phosphorylase from Clostridium thermocellum. Second, the secretion of Cel5-IA was improved by directed evolution with two novel double-layer Petri-dish-based high-throughput screening (HTS) methods. The high-sensitivity HTS relied on the detection of high-activity Cel5 on the carboxymethylcellulose/Congo-red assay. The second modest-sensitivity HTS focused on the detection of low-activity IA on the amylodextrin-I₂ assay. After six rounds of HTS, a secretory Cel5-IA level was increased to 234 mg/L, 155 times the wild-type IA with the NprB signal peptide only. This combinatory strategy could be useful to enhance the secretory production of large-size heterologous proteins in B. subtilis.     

A second Brazilian species of Ixocactus (Loranthaceae)

A large-leaved, apparently dioecious species ofIxocactus,I. macrophyllus, is described from Brazil.     

Tubulin Tyrosination Is Required for the Proper Organization and Pathfinding of the Growth Cone

Background

During development, neuronal growth cones integrate diffusible and contact guidance cues that are conveyed to both actin and microtubule (MT) cytoskeletons and ensure axon outgrowth and pathfinding. Although several post-translational modifications of tubulin have been identified and despite their strong conservation among species, their physiological roles during development, especially in the nervous sytem, are still poorly understood.

Methodology/Findings

Here, we have dissected the role of a post-translational modification of the last amino acid of the α-tubulin on axonal growth by analyzing the phenotype of precerebellar neurons in Tubulin tyrosin ligase knock-out mice (TTL ^−/−) through in vivo, ex vivo and in vitro analyses. TTL ^−/− neurons are devoid of tyrosinated tubulin. Their pathway shows defects in vivo, ex vivo, in hindbrains open-book preparations or in vitro, in a collagen matrix. Their axons still orient toward tropic cues, but they emit supernumerary branches and their growth cones are enlarged and exhibit an emission of mis-oriented filopodia. Further analysis of the TTL ^−/− growth cone intracellular organization also reveals that the respective localization of actin and MT filaments is disturbed, with a decrease in the distal accumulation of Myosin IIB, as well as a concomitant Rac1 over-activation in the hindbrain. Pharmacological inhibition of Rac1 over-activation in TTL ^−/− neurons can rescue Myosin IIB localization.

Conclusions/Significance

In the growth cone, we propose that tubulin tyrosination takes part in the relative arrangement of actin and MT cytoskeletons, in the regulation of small GTPases activity, and consequently, in the proper morphogenesis, organization and pathfinding of the growth cone during development.     

Delivery of Functionality in Complex Food Systems: Physically Inspired Approaches from Nanoscale to Microscale,Wageningen 18–21 October 2009

The Wageningen Delivery of Functionality symposium covered all aspects involved with food structural design to arrive at high-quality foods which meet demanding customer expectations and regulatory requirements. The symposium integrated aspects from the structural organization of foods at molecular and supramolecular scales to dedicated techniques required to describe and visualize such structures, the gastro-intestinal events and how to model these in a laboratory setting, and finally the impact those food structures and ingredients have on the consumer’s physiology and on the human perception. As an interdisciplinary platform, bringing together more than 160 researchers from academia and industry, the symposium meanwhile fulfills an important role in the food science community.     

The influence of natural rubber/Au nanoparticle membranes on the physiology of Leishmania brasiliensis

The development of nanotechnology has generated new means of disease diagnosis and treatment. Infectious diseases, including leishmaniasis, malaria, etc., have benefited from the advent of new nanomaterials and/or nanodevices capable of detecting specific antigens and antibodies with high specificity and low cost. In this paper, we present an investigation on a single-celled protozoan Leishmaniasis parasite, a disease considered of standard infectivity, given the high degree of immunological specificity. Natural rubber (NR) membranes incorporating gold nanoparticles (GNPs) were placed in the culture medium and the physiological behavior of Leishmania brasiliensis promastigotes was evaluated. The natural rubber membranes containing GNPs decreased the population growth rate, showing a lower index of living promastigotes (attached to the membrane surface) depending on the amount of nanoparticles deposited in the membrane surface. Such membranes may be used to develop a flexible band-aid for skin lesions from degenerative infection state, inhibiting the population growth of parasites in the lesions. In addition, natural rubber membranes would also stimulate angiogenesis in damaged tissues.