Programmable Polymorphism of a Virus-Like Particle

Virus-like particles (VLPs) have significant potential as both artificial vaccines and drug delivery systems. The ability to control their size has wide ranging utility, but achieving such controlled polymorphism using a single protein subunit is challenging as it requires altering VLP geometry. Here we achieve size control of MS2 bacteriophage VLPs via insertion of amino acid sequences in an external loop to shift its morphology to significantly larger forms. The resulting VLP size and geometry is controlled by altering the length and type of the insert used. Cryo-EM structures of the new VLPs, in combination with a kinetic model of their assembly, show that the abundance of wild type (T=3), T=4, D3 and D5 symmetrical VLPs can be controlled in this way. We propose a mechanism whereby the insert leads to a change in the dynamic behavior of the capsid protein dimer, affecting the interconversion between the symmetric and asymmetric conformers and thus determining VLP size and morphology.

Understanding SARS-CoV-2 budding through molecular dynamics simulations of M and E protein complexes

SARS-CoV-2 and other coronaviruses pose a major threat to global health, yet treatment efforts have largely ignored the process of envelope assembly, a key part of the coronaviral life cycle. When expressed together, the M and E proteins are sufficient to facilitate coronavirus envelope assembly. Envelope assembly leads to budding of coronavirus particles into the ER-Golgi intermediate compartment (ERGIC) and subsequent maturation of the virus, yet the mechanisms behind the budding process remain poorly understood. Better understanding of budding may enable new types of antiviral therapies. To this end, we ran atomistic molecular dynamics (MD) simulations of SARS-CoV-2 envelope assembly using the Feig laboratory's refined structural models of the M protein dimer and E protein pentamer. Our MD simulations consisted of M protein dimers and E protein pentamers in patches of virtual ERGIC membrane. By examining how these proteins induce membrane curvature in silico, we have obtained insights around how the budding process may occur. In our simulations, M protein dimers acted cooperatively to induce membrane curvature. By contrast, E protein pentamers kept the membrane planar. These results could help guide the development of novel antiviral therapeutics which inhibit coronavirus budding.

Theoretical Studies on the Binding Mode and Reaction Mechanism of TLP Hydrolase kpHIUH

In this work, we have investigated the binding conformations of the substrate in the active site of 5-HIU hydrolase kpHIUH and its catalytic hydrolysis mechanism. Docking calculations revealed that the substrate adopts a conformation in the active site with its molecular plane laying parallel to the binding interface of the protein dimer of kpHIUH, in which His7 and His92 are located adjacent to the hydrolysis site C6 and have hydrogen bond interactions with the lytic water. Based on this binding conformation, density functional theory calculations indicated that the optimal catalytic mechanism consists of two stages: (1) the lytic water molecule is deprotonated by His92 and carries out nucleophilic attack on C6=O of 5-HIU, resulting in an oxyanion intermediate; (2) by accepting a proton transferred from His92, C6–N5 bond is cleaved to completes the catalytic cycle. The roles of His7, His92, Ser108 and Arg49 in the catalytic reaction were revealed and discussed in detail.

In Silico Targeting DENV2's Prefusion Envelope Protein by Several Natural Products' Bioactive Compounds

Dengue caused by the dengue virus (DENV) is a severe health problem in tropical regions such as Southeast Asia, especially Indonesia. Indonesian have used rhizome as traditional medicine for 1300 years. This study investigated the compounds from Kaempferia galanga, Curcuma longa, Zingiber officinale, Curcuma aeruginosa, Curcuma zanthorrhiza, Alpinia galanga, and Allium sativum as antivirals agents, explicitly targeting the DENV envelope protein to inhibit viral fusion. This study involved 121 bioactive compounds and DENV2's prefusion envelope protein. The virtual screening and molecular docking were done through occupied the Lipinski rule of five checker (http://www.scfbio-iitd.res.in/software/drugdesign/lipinski.jsp) and AutoDock Vina (https://pyrx.sourceforge.io/) respectively. The top nine compounds with the strongest binding affinity were galangin, kampferide, demetoxy curcumin, bisdemethoxycurcumin, β-selinene, 6-(hydroxymethyl)-1,4,4-trimethylbicyclo[3.1.0]hexan-2-ol, piperine, estra-1,3, 5(10)-trien-17β-ol, and curcumin. These compounds' affinity values were significantly lower, around 45-62%, than chloroquine. Most of them interact with the kl hairpin and hydrophobic pocket formed by residues Val130, Leu135, Phe193, Leu198, and Phe279of critical domains that can interfere with the conformational change and rearrangement of protein dimer in the post-fusion stage. This study suggested that the galangin, demethoxycurcumin, and bisdemethoxycurcumin are considered the most potential compounds to be developed as anti-prefusion E DENV2 low-affinity and intense interaction with those. Keywords: DENV2, envelope protein, in silico, viral fusion, viral infection

DIMER HÓA PROTEIN DUNG HỢP VỚI RHAU BỞI CẤU TRÚC G-QUADRUPLEX SONG SONG

Protein dimer có vai trò quan trọng trong hoạt động sống của tế bào như hoạt hóa enzyme, truyền tín hiệu qua các thụ thể và điều hòa biểu hiện gen. Các phương pháp cảm ứng tạo protein dimer ra đời nhằm giúp con người chủ động trong việc điều hòa các quá trình sinh học. G-quadruplex là một phân tử có tiềm năng dimer hóa protein thông qua liên kết đặc hiệu với 2 phân tử protein RHAU. Tuy nhiên đến nay, chức năng này của G-quadruplex vẫn chưa được nghiên cứu rộng rãi. Trong nghiên cứu dưới đây, chúng tôi đã dòng hóa vector pTD14 mang gen mã hóa YFP dung hợp với protein RHAU và biểu hiện, tinh chế protein RHAU-YFP. Protein này cùng với protein RHAU-CFP được kiểm tra sự dimer hóa dưới sự cảm ứng bởi G-quadruplex thông qua phản ứng FRET. Kết quả cho thấy, vector pTD14 đã được dòng hóa thành công có thể được biểu hiện tạo protein RHAU-YFP trong điều kiện nhiệt độ 16OC, nồng độ IPTG 0,05 mM trong 24 giờ. Protein RHAU-YFP được tinh chế một lần qua cột His-Trap. Phản ứng FRET cho thấy G-quadruplex có khả năng cảm ứng dimer hóa protein RHAU-YFP và RHAU-CFP trong điều kiện thí nghiệm và nồng độ G-quadruplex 500 µM cho khả năng cảm ứng sự dimer hóa cao nhất. Các kết quả trên là tiền đề cho việc ứng dụng G-quadruplex để điều hòa các quá trình sinh học trong nghiên cứu y dược, bảo vệ sức khỏe con người.

All-Atom MD Simulations of the HBV Capsid Complexed with AT130 Reveal Secondary and Tertiary Structural Changes and Mechanisms of Allostery

The hepatitis B virus (HBV) capsid is an attractive drug target, relevant to combating viral hepatitis as a major public health concern. Among small molecules known to interfere with capsid assembly, the phenylpropenamides, including AT130, represent an important antiviral paradigm based on disrupting the timing of genome packaging. Here, all-atom molecular dynamics simulations of an intact AT130-bound HBV capsid reveal that the compound increases spike flexibility and improves recovery of helical secondary structure in the spike tips. Regions of the capsid-incorporated dimer that undergo correlated motion correspond to established sub-domains that pivot around the central chassis. AT130 alters patterns of correlated motion and other essential dynamics. A new conformational state of the dimer is identified, which can lead to dramatic opening of the intradimer interface and disruption of communication within the spike tip. A novel salt bridge is also discovered, which can mediate contact between the spike tip and fulcrum even in closed conformations, revealing a mechanism of direct communication across these sub-domains. Altogether, results describe a dynamical connection between the intra- and interdimer interfaces and enable mapping of allostery traversing the entire core protein dimer.

Two Be or Not Two Be: The Nuclear Autoantigen La/SS-B Is able to form Dimers and Oligomers in a Redox Dependent Manner

According to the literature, the autoantigen La is involved in Cap-independent translation. It was proposed that one prerequisite for this function is the formation of a protein dimer. However, structural analyses argue against La protein dimers. Noteworthy to mention, these structural analyses were performed under reducing conditions. Here we describe that La protein can undergo redox-dependent structural changes. The oxidized form of La protein can form dimers, oligomers and even polymers stabilized by disulfide bridges. The primary sequence of La protein contains three cysteine residues. Only after mutation of all three cysteine residues to alanine La protein becomes insensitive to oxidation, indicating that all three cysteines are involved in redox-dependent structural changes. Biophysical analyses of the secondary structure of La protein support the redox-dependent conformational changes. Moreover, we identified monoclonal anti-La antibodies (anti-La mAbs) that react with either the reduced or oxidized form of La protein. Differential reactivities to the reduced and oxidized form of La protein were also found in anti-La sera of autoimmune patients.

All-Atom MD Simulations of the HBV Capsid Complexed with AT130 Reveal Secondary and Tertiary Structural Changes and Mechanisms of Allostery

The hepatitis B virus (HBV) capsid is an attractive drug target, relevant to combating viral hepatitis as a major public health concern. Among small molecules known to interfere with capsid assembly, the phenylpropenamides, including AT130, represent an important anti-viral paradigm based on disrupting the timing of genome encapsulation. Crystallographic studies of AT130-bound complexes have been essential in explaining the effects of the small molecule on HBV capsid structure; however, computational examination reveals that key changes attributed to AT130 were erroneous, likely a consequence of interpreting poor resolution arising from a highly flexible protein. Here, all-atom molecular dynamics simulations of an intact AT130-bound HBV capsid reveal that, rather than damaging spike helicity, AT130 enhances the capsid’s ability to recover it. A new conformational state is identified, which can lead to dramatic opening of the intradimer interface and disruption of communication within the spike tip. A novel salt bridge is also discovered, which can mediate contact between the spike tip and fulcrum even in closed conformations, revealing a mechanism of direct communication across these domains. Combined with dynamical network analysis, results describe a connection between the intra- and interdimer interfaces and enable mapping of allostery traversing the entire capsid protein dimer.

A Perspective on Natural and Nature-Inspired Small Molecules Targeting Phosphodiesterase 9 (PDE9): Chances and Challenges against Neurodegeneration

As life expectancy increases, dementia affects a growing number of people worldwide. Besides current treatments, phosphodiesterase 9 (PDE9) represents an alternative target for developing innovative small molecules to contrast neurodegeneration. PDE inhibition promotes neurotransmitter release, amelioration of microvascular dysfunction, and neuronal plasticity. This review will provide an update on natural and nature-inspired PDE9 inhibitors, with a focus on the structural features of PDE9 that encourage the development of isoform-selective ligands. The expression in the brain, the presence within its structure of a peculiar accessory pocket, the asymmetry between the two subunits composing the protein dimer, and the selectivity towards chiral species make PDE9 a suitable target to develop specific inhibitors. Additionally, the world of natural compounds is an ideal source for identifying novel, possibly asymmetric, scaffolds, and xanthines, flavonoids, neolignans, and their derivatives are currently being studied. In this review, the available literature data were interpreted and clarified, from a structural point of view, taking advantage of molecular modeling: 3D structures of ligand-target complexes were retrieved, or built, and discussed.