Outer membrane protein folding from an energy landscape perspective

The cell envelope is essential for the survival of Gram-negative bacteria. This specialised membrane is densely packed with outer membrane proteins (OMPs), which perform a variety of functions. How OMPs fold into this crowded environment remains an open question. Here, we review current knowledge about OFMP folding mechanisms in vitro and discuss how the need to fold to a stable native state has shaped their folding energy landscapes. We also highlight the role of chaperones and the β-barrel assembly machinery (BAM) in assisting OMP folding in vivo and discuss proposed mechanisms by which this fascinating machinery may catalyse OMP folding

A unified model for BAM function that takes into account type Vc secretion and species differences in BAM composition

Transmembrane proteins in the outer membrane of Gram-negative bacteria are almost exclusively β-barrels. They are inserted into the outer membrane by a conserved and essential protein complex called the BAM (for β-barrel assembly machinery). In this commentary, we summarize current research into the mechanism of this protein complex and how it relates to type V secretion. Type V secretion systems are autotransporters that all contain a β-barrel transmembrane domain inserted by BAM. In type Vc systems, this domain is a homotrimer. We argue that none of the current models are sufficient to explain BAM function particularly regarding type Vc secretion. We also find that current models based on the well-studied model system Escherichia coli mostly ignore the pronounced differences in BAM composition between different bacterial species. We propose a more holistic view on how all OMPs, including autotransporters, are incorporated into the lipid bilayer

Labour market institutions and economic performance in the Netherlands

The central question of this article is whether or not effectiveness and efficiency are improved by the stronger reliance on markets given Dutch labour market institutions and their resulting corporatist wage formation. In answering this question, besides the influence on the production costs (neoclassical approach), we explicitly deal with and quantify the 'hidden' transaction costs (institutional economics approach) of more decentralized labour relations, flexibilization of the labour market, and working conditions 'a la carte'. The results presented cast doubt on both the efficiency and the effectiveness of recently introduced tailor-made solutions in the Dutch economy.Corporatism, economic performance, Netherlands, transaction costs,

Contradiction, circumvention and instrumentalization of noble values: How competition undermines the potential of alternatives

International audienc

Binding Interactions Between α-glucans from Lactobacillus reuteri and Milk Proteins Characterised by Surface Plasmon Resonance

Interactions between milk proteins and α-glucans at pH 4.0–5.5 were investigated by use of surface plasmon resonance. The α-glucans were synthesised with glucansucrase enzymes from Lactobacillus reuteri strains ATCC-55730, 180, ML1 and 121. Variations in the molecular characteristics of the α-glucans, such as molecular weight, linkage type and degree of branching, influenced the interactions with native and denatured β-lactoglobulin and κ-casein. The highest overall binding levels were reached with α-(1,4) compared to α-(1,3) linked glucans. Glucans withmany α-(1,6) linkages demonstrated the highest binding levels to κ-casein, whereas the interaction with native β-lactoglobulin was suppressed by α-(1,6) linkages. Glucans with a higher degree of branching generally displayed lower protein binding levels whereas a higher molecular weight resulted in increased binding to κ-casein. The interactions with κ-casein were not pH dependent, whereas binding to denatured β-lactoglobulin was highest at pH 4.0 and binding to native β-lactoglobulin was optimal at pH 4.5–5.0. This study shows that molecular weight, linkage type and degree of branching of α-glucans highly influence the binding interactions with milk proteins.