Cryo-EM structures of mitochondrial ABC transporter ABCB10 in apo and biliverdin-bound form.

ABCB10, a member of ABC transporter superfamily that locates in the inner membrane of mitochondria, plays crucial roles in hemoglobin synthesis, antioxidative stress and stabilization of the iron transporter mitoferrin-1. Recently, it was found that ABCB10 is a mitochondrial biliverdin exporter. However, the molecular mechanism of biliverdin export by ABCB10 remains elusive.

Effects of Coumarin on Rhizosphere Microbiome and Metabolome of .

Rhizosphere microorganisms can help plants absorb nutrients, coordinate their growth, and improve their environmental adaptability. Coumarin can act as a signaling molecule that regulates the interaction between commensals, pathogens, and plants. In this study, we elucidate the effect of coumarin on plant root microorganisms.

Footprinting Mass Spectrometry of Membrane Proteins: Ferroportin Reconstituted in Saposin A Picodiscs.

Membrane proteins participate in a broad range of cellular processes and represent more than 60% of drug targets. One approach to their structural analyses is mass spectrometry (MS)-based footprinting including hydrogen/deuterium exchange (HDX), fast photochemical oxidation of proteins (FPOP), and residue-specific chemical modification. Studying membrane proteins usually requires their isolation from the native lipid environment, after which they often become unstable.

Termini restraining of small membrane proteins enables structure determination at near-atomic resolution.

Small membrane proteins are difficult targets for structural characterization. Here, we stabilize their folding by restraining their amino and carboxyl termini with associable protein entities, exemplified by the two halves of a superfolder GFP. The termini-restrained proteins are functional and show improved stability during overexpression and purification.

Human ferroportin mediates proton-coupled active transport of iron.

As the sole iron exporter in humans, ferroportin controls systemic iron homeostasis through exporting iron into the blood plasma. The molecular mechanism of how ferroportin exports iron under various physiological settings remains unclear. Here we found that purified ferroportin incorporated into liposomes preferentially transports Fe2+ and exhibits lower affinities of transporting other divalent metal ions.

Open conformation of tetraspanins shapes interaction partner networks on cell membranes.

Tetraspanins, including CD53 and CD81, regulate a multitude of cellular processes through organizing an interaction network on cell membranes. Here, we report the crystal structure of CD53 in an open conformation poised for partner interaction. The large extracellular domain (EC2) of CD53 protrudes away from the membrane surface and exposes a variable region, which is identified by hydrogen-deuterium exchange as the common interface for CD53 and CD81 to bind partners.

Characterization of Warfarin Inhibition Kinetics Requires Stabilization of Intramembrane Vitamin K Epoxide Reductases.

Intramembrane enzymes are often difficult for biochemical characterization. Human vitamin K epoxide reductase (VKOR) is the target of warfarin. However, this intramembrane enzyme becomes insensitive to warfarin inhibition in vitro, preventing the characterization of inhibition kinetics for decades.

The Tetraspanin CD53 Regulates Early B Cell Development by Promoting IL-7R Signaling.

The tetraspanin CD53 has been implicated in B cell development and function. CD53 is a transcriptional target of EBF1, a critical transcription factor for early B cell development. Further, human deficiency of CD53 results in recurrent infections and reduced serum Igs.

Tmem178 negatively regulates store-operated calcium entry in myeloid cells via association with STIM1.

Store-operated calcium entry (SOCE) modulates cytosolic calcium in multiple cells. Endoplasmic reticulum (ER)-localized STIM1 and plasma membrane (PM)-localized ORAI1 are two main components of SOCE. STIM1:ORAI1 association requires STIM1 oligomerization, its re-distribution to ER-PM junctions, and puncta formation.

Membrane Protein Structure in Live Cells: Methodology for Studying Drug Interaction by Mass Spectrometry-Based Footprinting.

Mass spectrometry-based footprinting is an emerging approach for studying protein structure. Because integral membrane proteins are difficult targets for conventional structural biology, we recently developed a mass spectrometry (MS) footprinting method to probe membrane protein-drug interactions in live cells. This method can detect structural differences between apo and drug-bound states of membrane proteins, with the changes inferred from MS quantification of the cysteine modification pattern, generated by residue-specific chemical labeling.

Warfarin traps human vitamin K epoxide reductase in an intermediate state during electron transfer.

Although warfarin is the most widely used anticoagulant worldwide, the mechanism by which warfarin inhibits its target, human vitamin K epoxide reductase (hVKOR), remains unclear. Here we show that warfarin blocks a dynamic electron-transfer process in hVKOR. A major fraction of cellular hVKOR is in an intermediate redox state containing a Cys51-Cys132 disulfide, a characteristic accommodated by a four-transmembrane-helix structure of hVKOR.

[Synthesis and characterization of polylactide-based thermosetting polyurethanes with shape memory properties].

A series of bio-based thermosetting polyurethanes (Bio-PUs) were synthesized by the crosslinking reaction of polylactide and its copolymers diols with hexamethylene diisocyanate (HDI) trimer. The obtained Bio-PUs were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), universal tensile testing machine and cytotoxicity test. Results indicate that the PLA copolymer (P(LA-co-CL)) diols reduced the glass transition temperature (Tg) of Bio-PUs and improved their thermal stability, compared with PLA diols.

Structural and biochemical analyses of the Streptococcus pneumonia L,D-carboxypeptidase DacB.

The L,D-carboxypeptidase DacB plays a key role in the remodelling of Streptococcus pneumoniae peptidoglycan during cell division. In order to decipher its substrate-binding properties and catalytic mechanism, the 1.71 Å resolution crystal structure of DacB from S.

Structure of a novel O-linked N-acetyl-D-glucosamine (O-GlcNAc) transferase, GtfA, reveals insights into the glycosylation of pneumococcal serine-rich repeat adhesins.

Protein glycosylation catalyzed by the O-GlcNAc transferase (OGT) plays a critical role in various biological processes. In Streptococcus pneumoniae, the core enzyme GtfA and co-activator GtfB form an OGT complex to glycosylate the serine-rich repeat (SRR) of adhesin PsrP (pneumococcal serine-rich repeat protein), which is involved in the infection and pathogenesis. Here we report the 2.

Structural insights into SraP-mediated Staphylococcus aureus adhesion to host cells.

Staphylococcus aureus, a Gram-positive bacterium causes a number of devastating human diseases, such as infective endocarditis, osteomyelitis, septic arthritis and sepsis. S. aureus SraP, a surface-exposed serine-rich repeat glycoprotein (SRRP), is required for the pathogenesis of human infective endocarditis via its ligand-binding region (BR) adhering to human platelets.

Structures of the substrate-binding protein provide insights into the multiple compatible solute binding specificities of the Bacillus subtilis ABC transporter OpuC.

The compatible solute ABC (ATP-binding cassette) transporters are indispensable for acquiring a variety of compatible solutes under osmotic stress in Bacillus subtilis. The substrate-binding protein OpuCC (Opu is osmoprotectant uptake) of the ABC transporter OpuC can recognize a broad spectrum of compatible solutes, compared with its 70% sequence-identical paralogue OpuBC that can solely bind choline. To explore the structural basis of this difference of substrate specificity, we determined crystal structures of OpuCC in the apo-form and in complex with carnitine, glycine betaine, choline and ectoine respectively.

Crystal structure of the mucin-binding domain of Spr1345 from Streptococcus pneumoniae.

The surface protein Spr1345 from Streptococcus pneumoniae R6 is a 22-kDa mucin-binding protein (MucBP) involved in adherence and colonization of the human lung and respiratory tract. It is composed of a mucin-binding domain (MucBD) and a proline-rich domain (PRD) followed by an LPxTG motif, which is recognized and cleaved by sortase, resulting in a mature form of 171 residues (MF171) that is anchored to the cell wall. We found that the MucBD alone possesses comparable in vitro mucin-binding affinity to the mature form, and can be specifically enriched at the surface of human lung carcinoma A549 cells.