The C-terminal α-helix is crucial for the activity of the bacterial ABC transporter BmrA.

ABC transporters are membrane integral proteins that consist of a transmembrane (TMD) and nucleotide-binding domain (NBD). Two monomers (half-transporters) of the Bacillus subtilis ABC transporter BmrA (Bacillus multidrug-resistance ATP) dimerize to build a functional full-transporter. As all ABC exporters, BmrA uses the free energy of ATP hydrolysis to transport substrate molecules across the cell membrane.

Monomer unfolding of a bacterial ESCRT-III superfamily member is coupled to oligomer disassembly.

The inner membrane associated protein of 30 kDa (IM30), a member of the endosomal sorting complex required for transport (ESCRT-III) superfamily, is crucially involved in the biogenesis and maintenance of thylakoid membranes in cyanobacteria and chloroplasts. In solution, IM30 assembles into various large oligomeric barrel- or tube-like structures, whereas upon membrane binding it forms large, flat carpet structures. Dynamic localization of the protein in solution, to membranes and changes of the oligomeric states are crucial for its in vivo function.

Structural basis for Vipp1 membrane binding: from loose coats and carpets to ring and rod assemblies.

Vesicle-inducing protein in plastids 1 (Vipp1) is critical for thylakoid membrane biogenesis and maintenance. Although Vipp1 has recently been identified as a member of the endosomal sorting complexes required for transport III superfamily, it is still unknown how Vipp1 remodels membranes. Here, we present cryo-electron microscopy structures of Synechocystis Vipp1 interacting with membranes: seven structures of helical and stacked-ring assemblies at 5-7-Å resolution engulfing membranes and three carpet structures covering lipid vesicles at ~20-Å resolution using subtomogram averaging.

Dual Centrifugation-Based Screening for pH-Responsive Liposomes.

In liposomal drug delivery development, the delicate balance of membrane stability is a major challenge to prevent leakage (during shelf-life and blood circulation), and to ensure efficient payload release at the therapeutic destination. Our composite screening approach uses the processing by dual centrifugation technique to speed up the identification of de novo formulations of intermediate membrane stability. By screening binary lipid combinations at systemically varied ratios we highlight liposomal formulations of intermediate stability, what we termed "the edge of stability", requiring moderate stimuli for destabilization.

Structural basis for GTPase activity and conformational changes of the bacterial dynamin-like protein SynDLP.

SynDLP, a dynamin-like protein (DLP) encoded in the cyanobacterium Synechocystis sp. PCC 6803, has recently been identified to be structurally highly similar to eukaryotic dynamins. To elucidate structural changes during guanosine triphosphate (GTP) hydrolysis, we solved the cryoelectron microscopy (cryo-EM) structures of oligomeric full-length SynDLP after addition of guanosine diphosphate (GDP) at 4.

Structural plasticity of bacterial ESCRT-III protein PspA in higher-order assemblies.

Eukaryotic members of the endosome sorting complex required for transport-III (ESCRT-III) family have been shown to form diverse higher-order assemblies. The bacterial phage shock protein A (PspA) has been identified as a member of the ESCRT-III superfamily, and PspA homo-oligomerizes to form rod-shaped assemblies. As observed for eukaryotic ESCRT-III, PspA forms tubular assemblies of varying diameters.

Ultrasound-guided determination demonstrates influence of age, sex and type of sport on medial femoral condyle cartilage thickness in children and adolescents.

Purpose: To analyse the reliability of ultrasound-guided measurement of the cartilage thickness at the medial femoral condyle in athletically active children and adolescents before and after mechanical load in relation to age, sex and type of sport.

Methods: Three successive measurements were performed in 157 participants (median/min-max age: 13.1/6.

Conserved structures of ESCRT-III superfamily members across domains of life.

Structural and evolutionary studies of cyanobacterial phage shock protein A (PspA) and inner membrane-associated protein of 30 kDa (IM30) have revealed that these proteins belong to the endosomal sorting complex required for transport-III (ESCRT-III) superfamily, which is conserved across all three domains of life. PspA and IM30 share secondary and tertiary structures with eukaryotic ESCRT-III proteins, whilst also oligomerizing via conserved interactions. Here, we examine the structures of bacterial ESCRT-III-like proteins and compare the monomeric and oligomerized forms with their eukaryotic counterparts.

SynDLP is a dynamin-like protein of Synechocystis sp. PCC 6803 with eukaryotic features.

Dynamin-like proteins are membrane remodeling GTPases with well-understood functions in eukaryotic cells. However, bacterial dynamin-like proteins are still poorly investigated. SynDLP, the dynamin-like protein of the cyanobacterium Synechocystis sp.

Unfolding Individual Domains of BmrA, a Bacterial ABC Transporter Involved in Multidrug Resistance.

The folding and stability of proteins are often studied via unfolding (and refolding) a protein with urea. Yet, in the case of membrane integral protein domains, which are shielded by a membrane or a membrane mimetic, urea generally does not induce unfolding. However, the unfolding of α-helical membrane proteins may be induced by the addition of sodium dodecyl sulfate (SDS).

Cyanobacterial membrane dynamics in the light of eukaryotic principles.

Intracellular compartmentalization is a hallmark of eukaryotic cells. Dynamic membrane remodeling, involving membrane fission/fusion events, clearly is crucial for cell viability and function, as well as membrane stabilization and/or repair, e.g.

Hydrophobic mismatch and sequence specificity compete when transmembrane helix-helix interactions are measured with the TOXCAT assay.

Genetic assays capable of measuring the propensity of transmembrane helices to oligomerize within the cytoplasmic membrane of the bacterium are frequently used when sequence-specificity in transmembrane helix-helix interactions is investigated. In the present study, dimerization of the well-investigated wild-type and G83I-mutated transmembrane helix of the human glycophorin A protein was studied. Gradual prolongation of the transmembrane helix at the C-terminus with Leu residues lead to pronounced changes in the dimerization propensity when measured with the TOXCAT assay.

The Peripherally Membrane-attached Protein MbFACL6 of Mycobacterium tuberculosis Activates a Broad Spectrum of Substrates.

The infectious disease tuberculosis is one of the fifteen most common causes of death worldwide (according to the WHO). About every fourth person is infected with the main causative agent Mycobacterium tuberculosis (Mb). A characteristic of the pathogen is its entrance into a dormant state in which a phenotypic antibiotic resistance is achieved.

Membrane destabilization and pore formation induced by the Synechocystis IM30 protein.

The inner membrane-associated protein of 30 kDa (IM30) is essential in chloroplasts and cyanobacteria. The spatio-temporal cellular localization of the protein appears to be highly dynamic and triggered by internal as well as external stimuli, mainly light intensity. The soluble fraction of the protein is localized in the cyanobacterial cytoplasm or the chloroplast stroma, respectively.

CLiB - a novel cardiolipin-binder isolated data-driven and screening.

Cardiolipin, the mitochondria marker lipid, is crucially involved in stabilizing the inner mitochondrial membrane and is vital for the activity of mitochondrial proteins and protein complexes. Directly targeting cardiolipin by a chemical-biology approach and thereby altering the cellular concentration of "available" cardiolipin eventually allows to systematically study the dependence of cellular processes on cardiolipin availability. In the present study, physics-based coarse-grained free energy calculations allowed us to identify the physical and chemical properties indicative of cardiolipin selectivity and to apply these to screen a compound database for putative cardiolipin-binders.

Human Claudin-7 -Interactions Are Not Crucial for Membrane-Membrane (-) Interactions.

Human Claudin-7 (Cldn7) is a member of the Claudin (Cldn) superfamily. , these proteins form tight junctions, which establish constricted connections between cells. Cldns oligomerize within the membrane plane (= -interaction), and also interact with Cldns from adjacent cells (= -interaction).

Data-driven discovery of cardiolipin-selective small molecules by computational active learning.

Subtle variations in the lipid composition of mitochondrial membranes can have a profound impact on mitochondrial function. The inner mitochondrial membrane contains the phospholipid cardiolipin, which has been demonstrated to act as a biomarker for a number of diverse pathologies. Small molecule dyes capable of selectively partitioning into cardiolipin membranes enable visualization and quantification of the cardiolipin content.

Myristic Acid Inhibits the Activity of the Bacterial ABC Transporter BmrA.

ATP-binding cassette (ABC) transporters are conserved in all kingdoms of life, where they transport substrates against a concentration gradient across membranes. Some ABC transporters are known to cause multidrug resistances in humans and are able to transport chemotherapeutics across cellular membranes. Similarly, BmrA, the ABC transporter of is involved in excretion of certain antibiotics out of bacterial cells.

Increased stability of the TM helix oligomer abrogates the apoptotic activity of the human Fas receptor.

Human death receptors control apoptotic events during cell differentiation, cell homeostasis and the elimination of damaged or infected cells. Receptor activation involves ligand-induced structural reorganizations of preformed receptor trimers. Here we show that the death receptor transmembrane domains only have a weak intrinsic tendency to homo-oligomerize within a membrane, and thus these domains potentially do not significantly contribute to receptor trimerization.

Quantitative characterization of tetraspanin 8 homointeractions in the plasma membrane.

The spatial distribution of proteins in cell membranes is crucial for signal transduction, cell communication and membrane trafficking. Members of the Tetraspanin family organize functional protein clusters within the plasma membrane into so-called Tetraspanin-enriched microdomains (TEMs). Direct interactions between Tetraspanins are believed to be important for this organization.

Small Residues Inhibit Homo-Dimerization of the Human Carbonic Anhydrase XII Transmembrane Domain.

Amino acids with small side chains and motifs of small residues in a distance of four are rather abundant in human single-span transmembrane helices. While interaction of such helices appears to be common, the role of the small residues in mediating and/or stabilizing transmembrane helix oligomers remains mostly elusive. Yet, the mere existence of (small)xxx(small) motifs in transmembrane helices is frequently used to model dimeric TM helix structures.

PspA adopts an ESCRT-III-like fold and remodels bacterial membranes.

PspA is the main effector of the phage shock protein (Psp) system and preserves the bacterial inner membrane integrity and function. Here, we present the 3.6 Å resolution cryoelectron microscopy (cryo-EM) structure of PspA assembled in helical rods.

Binding and/or hydrolysis of purine-based nucleotides is not required for IM30 ring formation.

IM30, the inner membrane-associated protein of 30 kDa, is conserved in cyanobacteria and chloroplasts. Although its exact physiological function is still mysterious, IM30 is clearly essential for thylakoid membrane biogenesis and/or dynamics. Recently, a cryptic IM30 GTPase activity has been reported, albeit thus far no physiological function has been attributed to this.