Membrane protein crystal structure

Cholesterol from low-density lipoprotein (LDL) can be transported to many organelle membranes by non-vesicular mechanisms involving sterol transfer proteins (STPs). Fatty acid-binding protein (FABP) 7 was identified in our previous study searching for new regulators of intracellular cholesterol trafficking. Whether FABP7 is a bona fide STP remains unknown. Here, we found that FABP7 deficiency resulted in the accumulation of LDL-derived cholesterol in lysosomes and reduced cholesterol levels on the plasma membrane...

The tuberculosis (TB) emergency has been a pressing health threat for decades. With the emergence of drug resistant TB and complications from the COVID-19 pandemic, the TB health crisis is more serious than ever. Mycobacterium tuberculosis (Mtb), the causative agent of TB, requires iron for its survival. Thus, Mtb has evolved several mechanisms to acquire iron from the host. Mtb produces two siderophores, mycobactin and carboxymycobactin, which scavenge for host iron. Mtb siderophore-dependent iron acquisition requires the export of apo-siderophores from the cytosol to the host environment and import of iron-bound siderophores...

Ferroptosis is a recently discovered form of regulated cell death characterized by its distinct dependence on iron and the peroxidation of lipids within cellular membranes. Ferroptosis plays a crucial role in physiological and pathological situations and has attracted the attention of numerous scientists. Ferroptosis suppressive protein 1 (FSP1) is one of the main regulators that negatively regulates ferroptosis through the GPX4-independent FSP1-CoQ10-NAD(P)H axis and is a potential therapeutic target for ferroptosis-related diseases...

Promyelocytic leukemia (PML) nuclear bodies, membrane-less organelles in the nucleus, play a crucial role in cellular homeostasis. These dynamic structures result from the assembly of scaffolding PML proteins and various partners. Recent crystal structure analyses revealed essential self-interacting domains, while liquid-liquid phase separation contributes to their formation. PML bodies orchestrate post-translational modifications, particularly stress-induced SUMOylation, impacting target protein functions...

The high brightness and photostability of the green fluorescent protein StayGold make it a particularly attractive probe for long-term live-cell imaging; however, its dimeric nature precludes its application as a fluorescent tag for some proteins. Here, we report the development and crystal structures of a monomeric variant of StayGold, named mBaoJin, which preserves the beneficial properties of its precursor, while serving as a tag for structural proteins and membranes. Systematic benchmarking of mBaoJin against popular green fluorescent proteins and other recently introduced monomeric and pseudomonomeric derivatives of StayGold established mBaoJin as a bright and photostable fluorescent protein, exhibiting rapid maturation and high pH/chemical stability...

Desmosomes are multi-protein cell-cell adhesion structures supporting cell stability and mechanical stress resilience of tissues; best described in skin and heart. The kidney is exposed to various mechanical stimuli and stress, yet little is known about kidney desmosomes. In healthy kidneys, we found desmosomal proteins located at the apical-junctional complex in tubular epithelial cells. In four different animal models and patient biopsies with various kidney diseases, desmosomal components were significantly upregulated and partly miss-localized outside of the apical-junctional complexes along the whole lateral tubular epithelial cell membrane...

G-protein-coupled receptors (GPCRs) are structurally flexible membrane proteins that mediate a host of physiological responses to extracellular ligands like hormones and neurotransmitters. Fine features of their dynamic structural behavior are hypothesized to encode the functional plasticity seen in GPCR activity, where ligands with different efficacies can direct the same receptor toward different signaling phenotypes. Although the number of GPCR crystal structures is increasing, the receptors are characterized by complex and poorly understood conformational landscapes...

Malaria symptoms are associated with the asexual multiplication of Plasmodium falciparum within human red blood cells (RBCs) and fever peaks coincide with the egress of daughter merozoites following the rupture of the parasitophorous vacuole (PV) and the RBC membranes. Over the last two decades, it has emerged that the release of competent merozoites is tightly regulated by a complex cascade of events, including the unusual multi-step activation mechanism of the pivotal subtilisin-like protease 1 (Sub1) that takes place in three different cellular compartments and remains poorly understood...

BACKGROUND: Mucin 16 (MUC16) overexpression is linked with cancer progression, metastasis, and therapy resistance in high grade serous ovarian cancer and other malignancies. The cleavage of MUC16 forms independent bimodular fragments, the shed tandem repeat sequence which circulates as a protein bearing the ovarian cancer biomarker (CA125) and a proximal membrane-bound component which is critical in MUC16 oncogenic behavior. A humanized, high affinity antibody targeting the proximal ectodomain represents a potential therapeutic agent against MUC16 with lower antigenic potential and restricted human tissue expression...

The Ciona intestinalis voltage-sensing phosphatase (Ci-VSP) is a membrane protein containing a voltage-sensing domain (VSD) that is homologous to VSDs from voltage-gated ion channels responsible for cellular excitability. Previously published crystal structures of Ci-VSD in putative resting and active conformations suggested a helical-screw voltage sensing mechanism in which the S4 helix translocates and rotates to enable exchange of salt-bridge partners, but the microscopic details of the transition between the resting and active conformations remained unknown...

The membrane-associated solute-binding protein (SBP) MlaD of the maintenance of lipid asymmetry (Mla) system has been reported to help the transport of phospholipids (PLs) between the outer and inner membranes of Gram-negative bacteria. Despite the availability of structural information, the molecular mechanism underlying the transport of PLs and the ancestry of the protein MlaD remain unclear. In this study, we report the crystal structures of the periplasmic region of MlaD from Escherichia coli (EcMlaD) at a resolution range of 2...

The transmembrane glycoprotein angiotensin-converting enzyme 2 (ACE2) is a key component of the renin-angiotensin system (RAS). It was shown to be the receptor of severe acute respiratory syndrome coronavirus 2 in the COVID-19 outbreak (SARS-COV-2). Furthermore, ACE2 aids in the transport of amino acids across the membrane. ACE2 is lost from the membrane, resulting in soluble ACE2 (sACE2). We aim to examine the structural conformation alterations between SARS-CoV-1 or 2 variants at various periods with ACE2 from various sources, particularly in the area where it interacts with the viral protein and the receptor...

YejABEF is an ATP-binding cassette transporter that is implicated in the sensitivity of Escherichia coli to anti-microbial peptides, the best-characterized example being microcin C, a peptide-nucleotide antibiotic that targets aspartyl-tRNA synthetase. Here the structure of the extracellular solute binding protein, YejA, has been determined, revealing an oligopeptide-binding protein fold enclosing a ligand-binding pocket larger than those of other peptide-binding proteins of known structure. Prominent electron density in this cavity defines an undecapeptide sequence LGEPRYAFNFN, an observation that is confirmed by mass spectrometry...

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading threat to public health as it is resistant to most currently available antibiotics. Prodigiosin is a secondary metabolite of microorganisms with broad-spectrum antibacterial activity. This study identified a significant antibacterial effect of prodigiosin against MRSA with a minimum inhibitory concentration as low as 2.5 mg/L. The results of scanning electron microscopy, crystal violet staining, and confocal laser scanning microscopy indicated that prodigiosin inhibited biofilm formation in S...

Bacteria use the fatty acid composition of membrane lipids to maintain homeostasis of the bilayer. β-Ketoacyl-ACP synthase III (FabH) initiates fatty acid biosynthesis and is the primary determinant of the fatty acid composition. FabH condenses malonyl-acyl carrier protein with an acyl-Coenzyme A primer to form β -ketoacyl-acyl carrier protein which is used to make substrates for lipid synthesis. The acyl-Coenzyme A primer determines whether an acyl chain in the membrane has iso, anteiso, or no branching (straight chain) and biophysical properties of the membrane...

Planar cell polarity (PCP), essential to multicellular developmental processes, arises when cells polarize and align across tissues. Central to PCP is CELSR1, an atypical cadherin featuring a long ectodomain with nine extracellular cadherin (EC) repeats, a membrane adjacent domain (MAD10), and several characteristic adhesion GPCR domains. Cell-based aggregation assays have demonstrated CELSR1's homophilic adhesive nature, but mechanistic details are missing. Here, we investigate the possible adhesive properties and structures of CELSR1 EC repeats...

Subcellular compartments often serve to store nutrients or sequester labile or toxic compounds. As bacteria mostly do not possess membrane-bound organelles, they often have to rely on protein-based compartments. Encapsulins are one of the most prevalent protein-based compartmentalization strategies found in prokaryotes. Here, we show that desulfurase encapsulins can sequester and store large amounts of crystalline elemental sulfur. We determine the 1.78-angstrom cryo-EM structure of a 24-nanometer desulfurase-loaded encapsulin...

Proteins from the small multidrug resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in the metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea...

The LINC complex transmits cytoskeletal forces into the nucleus to control the structure and movement of nuclear contents. It is formed of nuclear SUN and cytoplasmic KASH proteins, which interact within the nuclear lumen, immediately below the outer nuclear membrane. However, the symmetrical location of KASH molecules within SUN-KASH complexes in previous crystal structures has been difficult to reconcile with the steric requirements for insertion of their immediately upstream transmembrane helices into the outer nuclear membrane...

This article describes the High-Pressure Freezing Laboratory for Macromolecular Crystallography (HPMX) at the ESRF, and highlights new and complementary research opportunities that can be explored using this facility. The laboratory is dedicated to investigating interactions between macromolecules and gases in crystallo, and finds applications in many fields of research, including fundamental biology, biochemistry, and environmental and medical science. At present, the HPMX laboratory offers the use of different high-pressure cells adapted for helium, argon, krypton, xenon, nitrogen, oxygen, carbon dioxide and methane...