α-Synuclein (α-syn) amyloid fibrils are the major component of Lewy bodies, which are the pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. High-resolution structure of α-syn fibril is important for understanding its assembly and pathological mechanism. Here, we determined a fibril structure of full-length α-syn (1-140) at the resolution of 3.07 Å by cryo-electron microscopy (cryo-EM). The fibrils are cytotoxic, and transmissible to induce endogenous α-syn aggregation in primary neurons. Based on the reconstructed cryo-EM density map, we were able to unambiguously build the fibril structure comprising residues 37-99. The α-syn amyloid fibril structure shows two protofilaments intertwining along an approximate 2 screw axis into a left-handed helix. Each protofilament features a Greek key-like topology. Remarkably, five out of the six early-onset PD familial mutations are located at the dimer interface of the fibril (H50Q, G51D, and A53T/E) or involved in the stabilization of the protofilament (E46K). Furthermore, these PD mutations lead to the formation of fibrils with polymorphic structures distinct from that of the wild-type. Our study provides molecular insight into the fibrillar assembly of α-syn at the atomic level and sheds light on the molecular pathogenesis caused by familial PD mutations of α-syn.

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MXenes are an emerging class of highly conductive two-dimensional (2D) materials with electrochemical storage features. Oriented macroscopic Ti3C2T x fibers can be fabricated from a colloidal 2D nematic phase dispersion. The layered conductive Ti3C2T x fibers are ideal candidates for constructing high-speed ionic transport channels to enhance the electrochemical capacitive charge storage performance. In this work, we assemble Ti3C2T x fibers with a high degree of flake orientation by a wet spinning process with controlled spinning speeds and morphology of the spinneret. In addition to the effects of cross-linking of magnesium ions between Ti3C2T x flakes, the electronic conductivity and mechanical strength of the as-prepared fibers have been improved to 7200 S cm–1 and 118 MPa, respectively. The oriented Ti3C2T x fibers present a volumetric capacitive charge storage capability of up to 1360 F cm–3 even in a Mg-ion based neutral electrolyte, with contributions from both nanofluidic ion transport and Mg-ion intercalation pseudocapacitance. The oriented 2D Ti3C2T x driven nanofluidic channels with great electronic conductivity and mechanical strength endows the MXene fibers with attributes for serving as conductive ionic cables and active materials for fiber-type capacitive electrochemical energy storage, biosensors, and potentially biocompatible fibrillar tissues.

Drugs that target the human serotonin 2A receptor (5-HT 2A R) are used to treat neuropsychiatric diseases; however, many have hallucinogenic effects, hampering their use. Here, we present structures of 5-HT 2A R complexed with the psychedelic drugs psilocin (the active metabolite of psilocybin) and d -lysergic acid diethylamide (LSD), as well as the endogenous neurotransmitter serotonin and the nonhallucinogenic psychedelic analog lisuride. Serotonin and psilocin display a second binding mode in addition to the canonical mode, which enabled the design of the psychedelic IHCH-7113 (a substructure of antipsychotic lumateperone) and several 5-HT 2A R β-arrestin–biased agonists that displayed antidepressant-like activity in mice but without hallucinogenic effects. The 5-HT 2A R complex structures presented herein and the resulting insights provide a solid foundation for the structure-based design of safe and effective nonhallucinogenic psychedelic analogs with therapeutic effects.

Phosphatidylinositol phosphates (PIPs) and cholesterol are known to regulate the function of late endosomes and lysosomes (LELs), and ORP1L specifically localizes to LELs. Here, we show in vitro that ORP1 is a PI(4,5)P2- or PI(3,4)P2-dependent cholesterol transporter, but cannot transport any PIPs. In cells, both ORP1L and PI(3,4)P2 are required for the efficient removal of cholesterol from LELs. Structures of the lipid-binding domain of ORP1 (ORP1-ORD) in complex with cholesterol or PI(4,5)P2 display open conformations essential for ORP function. PI(4,5)P2/PI(3,4)P2 can facilitate ORP1-mediated cholesterol transport by promoting membrane targeting and cholesterol extraction. Thus, our work unveils a distinct mechanism by which PIPs may allosterically enhance OSBP/ORPs-mediated transport of major lipid species such as cholesterol.

Plasminogen activator inhibitor-1 (PAI-1), together with its physiological target urokinase-type plasminogen activator (uPA), plays a pivotal role in fibrinolysis, cell migration, and tissue remodeling and is currently recognized as being among the most extensively validated biological prognostic factors in several cancer types. PAI-1 specifically and rapidly inhibits uPA and tissuetype PA (tPA). Despite extensive structural/functional studies on these two reactions, the underlying structural mechanism has remained unknown due to the technical difficulties of obtaining the relevant structures. Here, we report a strategy to generate a PAI-1⅐uPA(S195A) Michaelis complex and present its crystal structure at 2.3-Å resolution. In this structure, the PAI-1 reactive center loop serves as a bait to attract uPA onto the top of the PAI-1 molecule. The P4 -P3 residues of the reactive center loop interact extensively with the uPA catalytic site, accounting for about two-thirds of the total contact area. Besides the active site, almost all uPA exosite loops, including the 37-, 60-, 97-, 147-, and 217-loops, are involved in the interaction with PAI-1. The uPA 37-loop makes an extensive interaction with PAI-1 ␤-sheet B, and the 147-loop directly contacts PAI-1 ␤-sheet C. Both loops are important for initial Michaelis complex formation. This study lays down a foundation for understanding the specificity of PAI-1 for uPA and tPA and provides a structural basis for further functional studies.

Single-particle cryo-electron microscopy (cryo-EM) has become one of the most essential tools to understand biological mechanisms at molecular level. A major bottleneck in cryo-EM technique is the preparation of good specimens that embed biological macromolecules in a thin layer of vitreous ice. In the canonical cryo-EM specimen preparation method, biological macromolecules tend to be adsorbed to the air–water interface, causing partial denaturation and/or preferential orientations. In this work, we have designed and produced a new type of cryo-EM grids using bioactive-ligand functionalized single-crystalline monolayer graphene membranes as supporting films. The functionalized graphene membrane (FGM) grids exhibit specific binding affinity to histidine (His)-tagged proteins and complexes. In cryo-EM, the FGM grids generate relatively low background for imaging and selectively anchor 20S proteasomes to the supporting film surface, enabling near-atomic-resolution 3D reconstruction of the complex. We envision that the FGM grids could benefit single particle cryo-EM specimen preparation with high reproducibility and robustness, therefore enhancing the efficiency and throughput of high-resolution cryo-EM structural determination.

Background: Glucose can glycate human serum albumin (HSA), but the mechanism is unknown. Results: Crystal structures of rHSA in the presence of glucose show that glucose is linearized and covalently linked to rHSA. Conclusion:The residues Lys-195 and Lys-199 of rHSA are involved in glucose ring opening. Significance: This work provides a structural mechanism of protein glycation.