Export Channel Research Articles

Structural Dynamics of the Functional Nonameric Type III Translocase Export Gate

Type III protein secretion is widespread in Gram-negative pathogens. It comprises the injectisome with a surface-exposed needle and an inner membrane translocase. The translocase contains the SctRSTU export channel enveloped by the export gate subunit SctV that binds chaperone/exported clients and forms a putative ante-chamber. We probed the assembly, function, structure and dynamics of SctV from enteropathogenic E. coli (EPEC). In both EPEC and E. coli lab strains, SctV forms peripheral oligomeric clusters that are detergent-extracted as homo-nonamers. Membrane-embedded SctV9 is necessary and sufficient to act as a receptor for different chaperone/exported protein pairs with distinct C-domain binding sites that are essential for secretion. Negative staining electron microscopy revealed that peptidisc-reconstituted His-SctV9 forms a tripartite particle of ∼22 nm with a N-terminal domain connected by a short linker to a C-domain ring structure with a ∼5 nm-wide inner opening. The isolated C-domain ring was resolved with cryo-EM at 3.1 Å and structurally compared to other SctV homologues. Its four sub-domains undergo a three-stage “pinching” motion. Hydrogen-deuterium exchange mass spectrometry revealed this to involve dynamic and rigid hinges and a hyper-flexible sub-domain that flips out of the ring periphery and binds chaperones on and between adjacent protomers. These motions are coincident with local conformational changes at the pore surface and ring entry mouth that may also be modulated by the ATPase inner stalk. We propose that the intrinsic dynamics of the SctV protomer are modulated by chaperones and the ATPase and could affect allosterically the other subunits of the nonameric ring during secretion.

Entrepreneurial orientation, export channel selection, and export performance of SMEs

Although research indicates that the export channel a firm uses can significantly impact export performance, it is unclear how firms should select this channel. Models of export channel choice tend to concentrate on transaction cost efficiencies, ignoring value adding orientations that entrepreneurial firms may possess. In this paper we develop and test the theoretical notion that in addition to transaction costs, differences in entrepreneurial orientation (EO) influence export channel choice and as a consequence export performance. Using data from a sample of Dutch and Italian SMEs we find that adding EO (moderated by institutional distance) significantly improves our model of export channel choice. Further we find that firms selecting export channels that align not only with transaction cost factors but also firm level EO, moderated by institutional distance, have higher export market performance. Thus, our study adds to and extends the export channel choice literature and provides interesting new insights into how EO helps firms create more successful export operations.

Which export channels provide real options to SMEs?

Real option logic helps managers create value when making decisions because it focuses on managing the uncertainty concerning potential upside benefits and downside risks of an investment. Yet there is little research looking at the real option consequences of making export channel investments. We propose that export channel investments vary in their ability to provide real options and present a novel classification of real option export channels. We suggest that when faced with high uncertainty SMEs will prefer simpler real option export channels over more complex options. We also theorize that firm-level strategic flexibility (i.e. the depth and breadth of export experience) negatively moderates the relationship between uncertainty and real option export channel choice. Based on a sample of Austrian exporting SMEs, we find some support for our propositions. Hence, we contribute to the real option and export channel literatures by providing new insights into how export channel decisions are made and how firms choose between different real option alternatives.

Export resilience – A future key success factor for Upper Austrian B2B companies?

Motivation: Seeing Upper Austrian B2B companies struggle in keeping up their export business intensity and simultaneously accelerating the usage of digital communication and export channels, creates the starting point for an Export Resilience study in Upper Austria, an export-oriented region. The main motivation for implementing a study in this particular field was the creation of a pool of current key findings, ring-fenced by clear managerial implications and recommendations, which respond to future export trends emerging out of the study. Findings: An online questionnaire was sent out to exporting B2B companies which was completed by 173 respondents. The data provides insights in triggers of export resilience, insight in future export channels and differences in the export strategy of Upper Austrian B2B companies. For example, the survey has shown that 52% of the participating businesses can be classified as being „immune” to external influences. Further insights are given according to the change of digital export tools, the form of meetings and AI based export tools. Conclusion: Consequently, the extent to which the implementation of the export resilience study stimulated the dialogue between the academic and business community led to managerial recommendations for Austrian B2B export companies.

ANALYSIS OF INTERNAL LOGISTIC COST ON EXPORTS OF PERUVIAN COFFEE IN THE PERIOD 2015 – 2019

The objective of the research was to analyse the main components of internal logistics costs that are shown in the process of Peruvian coffee exports in the period 2015-2019. This study used various government sources, document review, and extraction of information systems. To do this we take into account 6 departments with greater coffee production, connected with three logistics corridors that have as a starting point the production areas and reach the export channels of Callao and Paita. Also, using the information gathered from the logistics performance index, a brief internal transport comparison was made between Peru and Colombia. As a result, the logistic cost of both countries is higher than 14.1% (Latin American average), taking into account that in both countries the only internal logistic component in which they coincide is transportation. It is concluded that national transportation hurts impact on logistics costs, since these are affected in the final price of coffee and the profitability of the Peruvian farmer.

The (In)applicability of the Right of Innocent Passage in the Gulf of Finland – Russia’s Return to a Mare Clausum?

Abstract The Gulf of Finland has one of the busiest shipping routes globally and is the main export channel for Russian oil and gas. The Russian Federation has not closed its territorial sea for the east-west passage of ships to and from its ports. However, it has blocked over the past dozen years the north-south passage of an Estonian-Finnish commercial ferry line that has not received the Russian Federation’s permission for crossing its territorial sea. The Russian Federation’s permit-based passage regime caused the closure of that ferry line in 2007 and reportedly still hinders its re-establishment. In this context, the Russian Federation’s practice on the right of innocent passage through its territorial sea in the Gulf of Finland resembles the Soviet Union’s practice prior to the 1989 Jackson Hole statement.

BamA forms a translocation channel for polypeptide export across the bacterial outer membrane

The β-barrel assembly machine (BAM) integrates β-barrel proteins into the outer membrane (OM) of Gram-negative bacteria. An essential BAM subunit (BamA) catalyzes integration by promoting the formation of a hybrid-barrel intermediate state between its own β-barrel domain and that of its client proteins. Here we show that in addition to catalyzing the integration of β-barrel proteins, BamA functions as a polypeptide export channel. Invivo structural mapping via intermolecular disulfide crosslinking showed that the extracellular "passenger" domain of a member of the "autotransporter" superfamily of virulence factors traverses the OM through the BamA β-barrel lumen. Furthermore, we demonstrate that a highly conserved residue within autotransporter β-barrels is required to position the passenger inside BamA to initiate translocation and that during translocation, the passenger stabilizes the hybrid-barrel state. Our results not only establish a new function for BamA but also unify the divergent functions of BamA and other "Omp85" superfamily transporters.

Intermediary resources and export venture performance under different export channel structures

PurposeThe literature on export channels suggests that intermediary resources, namely intermediary competence and availability, are critical for export success. However, little is known about how the beneficial effects of intermediary resources differ amongst integrated, independent and dual channel structures. One difference between these channel structures is the degree of reliance on independent intermediaries. This study aims to investigate (1) the impact of intermediary resources on export venture success, that is, export sales performance and channel maintenance costs and (2) the moderating role of the degree of reliance on independent intermediaries.Design/methodology/approachEmpirical testing was conducted using survey data collected from 204 Japanese industrial exporting ventures. To test the proposed hypotheses, this study estimated a structural equation model with the maximum likelihood estimation procedure.FindingsEvidence shows that two aspects of intermediary resources have different beneficial effects on export venture success. Specifically, intermediary availability leads to export venture success by decreasing channel maintenance costs, whereas intermediary competence is not always beneficial for it. Furthermore, this study finds that reliance on independent intermediaries positively moderates the impacts of intermediary competence and availability.Originality/valuePrevious studies emphasise the importance of intermediary resources and export channel structures. However, the question of whether export channel structures determine the performance benefits of intermediary resources is unanswered. By addressing this question, this study provides helpful insight into how exporting managers can implement channel strategy and access intermediary resources to achieve export success.

CURRENT STATE OF THE GRAIN MARKET AND TRENDS OF ITS DEVELOPMENT

The article outlines the role of the grain market, assesses its condition, identifies trends and develops new scientific approaches to strategic areas of improvement and development of the grain market, which will help overcome the information asymmetry of the market environment.It is noted that the grain market forms the basis of food security and significantly affects the living standards of the population, so qualitative and quantitative indicators of its condition, development trends are of strategic importance for the entire national economy, as it is a crucial prerequisite for sustainable growth. It is substantiated that the need for state regulation of the grain market is associated with the rapid growth of production of cereals and legumes, which generates additional challenges and problems, among which are the following: intensification of competition in global markets; lower world prices and, accordingly, falling export revenues; lack of capacity and storage space for reliable storage and quality processing of grain and their obsolescence; logistical capacity of domestic ports and rail transport; limited distribution channels; modern agricultural innovative technologies, providing high productivity, contribute to increasing unemployment in rural areas; low capacity of processing plants; deformation of traditional production chains. In addition, it should be emphasized that the COVID-19 pandemic has provoked a decline in incomes. The following directions of development of the grain market are defined: increase of transparency of the grain market; strengthening the importance of the state agent in the grain market; expansion of grain export channels; diversification of grain use areas; expanding the financial capabilities of grain producers; improving information support for the functioning of the grain market; increasing the effectiveness of state support programs; establishment of reliable distribution channels; assistance in entering world grain markets; formation of a protectionist environment for domestic grain market participants; creation of a favorable regulatory field for grain producers; timely provision of necessary public services in a pandemic.

Technology licensing, entry mode, and trade liberalization

AbstractThis study considers the interactions among technology licensing, entry mode, and trade liberalization in a licensing model of strategic commitment. Prior to the licensing agreement, an insider innovator offers the licensee a contract that may restrict the innovator to the use of generic technology, while allowing the licensee to access state‐of‐the‐art technology. An insider innovator can enter the domestic market through either the export or foreign direct investment (FDI) channels. In this context, we characterize the optimal entry mode and the associated licensing schemes of the foreign firm in the presence of a tariff reduction. We show that a tariff reduction may switch the optimal entry mode of the foreign firm from exporting to FDI and can be detrimental to the domestic welfare of the host country and the profit of both firms.

Impact of Trade Liberalization on Household Welfare: An Analysis Using Household Exposure-to-Trade Indices

This paper quantifies the impact of trade liberalization at the household level using data from the Vietnam Household Living Standard Survey from 2002 to 2016. Household welfare is measured using income, expenditure, and vulnerability to poverty. Unlike previous studies, we address potential endogeneity at the household level by constructing household exposure-to-trade indices as a proxy for trade liberalization. These indices are advantageous as they capture the influence of trade liberalization at the national level and the households’ ability to respond to new opportunities. The results suggest that trade liberalization improves Vietnamese household income and expenditure via the export channel or the expansion of labor demand. Tariff reduction for exported goods is less favorable to household welfare. The impact of trade liberalization became smaller and less significant after the global downturn in 2008. Rural households suffered more vulnerability from trade, and the poor gained fewer benefits after the financial crisis in 2008.

A structure-function study of C-terminal residues predicted to line the export channel in Salmonella Flagellin

BackgroundStructural studies of a Salmonella Typhimurium flagellin protein indicated that four polar or charged C-terminal amino acid residues line the inner channel of the flagellum. The hydrophilic character of these putative channel-lining residues was predicted to be essential to facilitate the transport of unfolded flagellin monomers during flagellar assembly. The structure-function relationship of these putative channel-lining residues was investigated by site-directed mutagenesis to examine effects of side chain polarity and size on flagella assembly and function. MethodsChannel-lining residue variants were generated using site-directed mutagenesis to substitute alanine and other residues to examine the effects of altered side-chain polarity on export and assembly. The export, in vivo motility function, and flagellar structure of variants was characterized by agar motility, video microscopy, immunofluorescence, and SDS-PAGE. ResultsAlanine substitution yielded decreased motility and flagellar assembly for three of the four residues. However, alanine substitution of residue Arg 494 did not alter export, although substitution with negatively charged glutamate decreased motility and flagellar filament length. Furthermore, many of the C-terminal mutations affected flagellar filament morphology and stability, often resulting in more tightly coiled and/or more brittle flagella than the wild type. ConclusionsThe four channel-lining C-terminal residues may facilitate monomer protein transport but also have structural roles in determining the stability and morphology of the flagellum. General significanceThese results provide further insight into the complex process of bacterial flagellin export and flagellar assembly and provide evidence of previously unknown structural functions for the four putative channel-lining residues.

A gateway to the cytosol

Coronavirus Coronaviruses transform host cell membranes into peculiar double-membrane vesicles that have long been thought to accommodate viral genome replication. However, because these compartments appeared to be completely sealed, it has remained unknown how the newly made viral RNA could be exported to the cytosol for translation and packaging into new virions. Wolff et al. used cryo–electron microscopy to identify a molecular pore that spans the double membrane (see the Perspective by Unchwaniwala and Ahlquist). Six copies of a large coronavirus transmembrane protein formed the core of this structure, which may constitute a viral RNA export channel and provide a target for future antiviral interventions. Science , this issue p. [1395][1]; see also p. [1306][2] [1]: /lookup/doi/10.1126/science.abd3629 [2]: /lookup/doi/10.1126/science.abe0322

Contacting domains segregate a lipid transporter from a solute transporter in the malarial host\u2013parasite interface

The malaria parasite interfaces with its host erythrocyte (RBC) using a unique organelle, the parasitophorous vacuole (PV). The mechanism(s) are obscure by which its limiting membrane, the parasitophorous vacuolar membrane (PVM), collaborates with the parasite plasma membrane (PPM) to support the transport of proteins, lipids, nutrients, and metabolites between the cytoplasm of the parasite and the cytoplasm of the RBC. Here, we demonstrate that the PV has structure characterized by micrometer-sized regions of especially close apposition between the PVM and the PPM. To determine if these contact sites are involved in any sort of transport, we localize the PVM nutrient-permeable and protein export channel EXP2, as well as the PPM lipid transporter PfNCR1. We find that EXP2 is excluded from, but PfNCR1 is included within these regions of close apposition. We conclude that the host-parasite interface is structured to segregate those transporters of hydrophilic and hydrophobic substrates.

Inequality in Latin America: the role of the nature of trade and partners

AbstractThis paper investigates the relationship between trade openness and income inequality in 11 Latin American countries over the period 1989–2015. The authors use a panel dynamic approach to take into account the high persistence of income inequality. The analysis classifies trade flows, exports and imports according to trading partner’s income level. Then, the authors split trade flows according to different stages of production. The results show that overall trade flows do not statistically affect income inequality in Latin America. However, trade has divergent effects depending on the trade partners: trade with similar- and lower-income countries exacerbates inequality, while trade with higherincome countries reduces income dispersion. The results also emphasise the role of the export channel (in particular in primary commodities) in explaining income inequality in Latin American countries and imports of consumption goods seem to matter more than imports of intermediate and capital goods.

Amyloidogenic processing of Alzheimer's disease β-amyloid precursor protein induces cellular iron retention.

The proteolytic cleavage of β-amyloid precursor protein (APP) to form the amyloid beta (Aβ) peptide is related to the pathogenesis of Alzheimer's disease (AD) because APP mutations that influence this processing either induce familial AD or mitigate the risk of AD. Yet Aβ formation itself may not be pathogenic. APP promotes neuronal iron efflux by stabilizing the cell-surface presentation of ferroportin, the only iron export channel of cells. Mislocalization of APP can promote iron retention, thus we hypothesized that changes in endocytotic trafficking associated with altered APP processing could contribute to the neuronal iron elevation and oxidative burden that feature in AD pathology. Here, we demonstrate, using genetic and pharmacological approaches, that endocytotic amyloidogenic processing of APP impairs iron export by destabilizing ferroportin on the cell surface. Conversely, preferential non-amyloidogenic processing of APP at the cell surface promotes ferroportin stabilization to decrease intraneuronal iron. A new Aβ-independent hypothesis emerges where the amyloidogenic processing of APP, combined with age-dependent iron elevation in the tissue, increases pro-oxidant iron burden in AD.

FliI6-FliJ molecular motor assists with unfolding in the type III secretion export apparatus

The role of rotational molecular motors of the ATP synthase class is integral to the metabolism of cells. Yet the function of FliI6-FliJ complex, a homolog of the F1 ATPase motor, within the flagellar export apparatus remains unclear. We use a simple two-state model adapted from studies of linear molecular motors to identify key features of this motor. The two states are the ‘locked’ ground state where the FliJ coiled coil filament experiences angular fluctuations in an asymmetric torsional potential, and a ‘free’ excited state in which FliJ undergoes rotational diffusion. Michaelis-Menten kinetics was used to treat transitions between these two states, and obtain the average angular velocity of the unloaded FliJ filament within the FliI6 stator: ωmax ≈ 9.0 rps. The motor was then studied under external counter torque conditions in order to ascertain its maximal power output: Pmax ≈ 42 kBT/s (or 102 kW/mol), and the stall torque: Gstall ≈ 3 kBT/rad (or 0.01 nN·nm/rad). Two modes of action within the flagellar export apparatus are proposed, in which the motor performs useful work either by continuously ‘grinding’ through the resistive environment of the export gate, or by exerting equal and opposite stall force on it. In both cases, the resistance is provided by flagellin subunits entering the flagellar export channel prior to their unfolding. We therefore propose that the function of the FliI6-FliJ complex is to lower the energy barrier, and therefore assist in unfolding of the flagellar proteins before feeding them into the transport channel.

Development of a novel recombinant cell line for detection and characterization of Ah receptor nuclear translocation in intact cells

The Ah receptor (AhR) is a ligand-dependent transcriptional factor that mediates the effects of structurally diverse chemicals. Ligand binding stimulates nuclear translocation of the AhR and leads to AhR DNA binding and increased gene expression. Studies of the molecular mechanisms by which ligands bind to and activate the AhR and AhR-dependent signal transduction require methods to easily examine each step of the AhR signaling pathway. While current assays can measure ligand and DNA binding in vitro and gene expression in cells, there is no simple method to monitor AhR nuclear translocation. We developed a stably transfected mouse hepatoma cell line (yAHAYc6) that expresses yellow fluorescent protein-tagged AhR (yAhR) for use in qualitative or semiquantitative assessment of nuclear/cytoplasmic distribution of yAhR in living cells by fluorescent microscopy. yAhR nuclear translocation was stimulated in a concentration- and time-dependent manner by AhR agonists and inhibited by antagonists. Inhibition of nuclear export channels by leptomycin B, resulted in increased nuclear accumulation of yAhR in the absence of added ligand, indicating endogenous nucleocytoplasmic shuttling of unliganded AhR and demonstrating the utility of these cells. This novel cell line can be used to detect and characterize AhR ligands and will facilitate mechanistic studies of AhR signaling.

Marketing of baobab pulp in Kenya: Collectors’ choice of rural versus urban markets

Baobab products provide cash income and supplement diets for local communities living in marginalised, arid and semi-arid regions. However, these products are neglected by research, selectively traded and considered underutilised. This study endeavours to narrow this information gap by analysing the determinants of baobab collectors’ choice of marketing channels in Kenya. A multinomial logit was employed, using a dataset of 268 baobab collectors from three counties. The results show that the majority of baobab collectors sell their baobab pulp through rural markets (assemblers and rural wholesalers), as opposed to urban buyers (urban wholesalers, retailers and processors). Export channels are conspicuously missing from the chain. Human capital and transactional and institutional factors significantly influence the collectors’ choice of marketing channels. The results reveal that building capacity around market development, research and education, road networks and institutional services is essential to create more profitable channels for generating income, enhancing food security and reducing malnutrition.

Growth, Distribution, and External Constraints: A Post-Kaleckian Model Applied to Brazil

ABSTRACT The purpose of this research is to analyze whether the Brazilian economy behaved under a wage-led or profit-led regime between 1960 and 2011, considering a Post-Kaleckian model in a context of external constraints. The time span is limited by data availability (i.e., 2011). To answer the question of whether the Brazilian economy works under a wage-led or profit-led regime, we propose a simple Post-Kaleckian model. The model suggests that a profit-led regime is more probable for Brazil. Moreover, a wage-led regime occurs when a balance of payments constrained growth model is taken into consideration. Likewise, the real exchange rate has a positive impact on economic growth through the export channel. This result is a novelty in the recent literature about the relationship between real exchange rate and economic growth within a Post-Kaleckian model. The Brazilian economy was chosen as it is one of the biggest economies in Latin America.