Combinatorial synthesis of a hyaluronan based polysaccharide library for enhanced CD44 binding.

Hyaluronan (HA) plays important roles in a wide range of biological events. The principal receptor of HA in the human body is the Cluster of Differentiation 44 (CD44). To enhance the binding between HA and CD44, a new approach was designed to take advantage of the four-component Ugi reaction.

Characterization of caspase-2 inhibitors based on specific sites of caspase-2-mediated proteolysis.

Since the discovery of the caspase-2 (Casp2)-mediated ∆tau314 cleavage product and its associated impact on tauopathies such as Alzheimer's disease, the design of selective Casp2 inhibitors has become a focus in medicinal chemistry research. In the search for new lead structures with respect to Casp2 selectivity and drug-likeness, we have taken an approach by looking more closely at the specific sites of Casp2-mediated proteolysis. Using seven selected protein cleavage sequences, we synthesized a peptide series of 53 novel molecules and studied them using in vitro pharmacology, molecular modeling, and crystallography.

Structure-Based Design and Biological Evaluation of Novel Caspase-2 Inhibitors Based on the Peptide AcVDVAD-CHO and the Caspase-2-Mediated Tau Cleavage Sequence YKPVD314.

Alzheimer's disease (AD) was first described by Alois Alzheimer over 100 years ago, but there is still no overarching theory that can explain its cause in detail. There are also no effective therapies to treat either the cause or the associated symptoms of this devastating disease. A potential approach to better understand the pathogenesis of AD could be the development of selective caspase-2 (Casp2) probes, as we have shown that a Casp2-mediated cleavage product of tau (Δtau314) reversibly impairs cognitive and synaptic function in animal models of tauopathies.

Structural Characterization of the Human Cytosolic Malate Dehydrogenase I.

The first crystal structure of the human cytosolic malate dehydrogenase I (MDH1) is described. Structure determination at a high resolution (1.65 Å) followed production, isolation, and purification of human MDH1 using a bacterial expression system.

Structure and Functional Characterization of Human Histidine Triad Nucleotide-Binding Protein 1 Mutations Associated with Inherited Axonal Neuropathy with Neuromyotonia.

Inherited peripheral neuropathies are a group of neurodegenerative disorders that clinically affect 1 in 2500 individuals. Recently, genetic mutations in human histidine nucleotide-binding protein 1 (hHint1) have been strongly and most frequently associated with patients suffering from axonal neuropathy with neuromyotonia. However, the correlation between the impact of these mutations on the hHint1 structure, enzymatic activity and in vivo function has remained ambiguous.

A Crystal Structure Based Guide to the Design of Human Histidine Triad Nucleotide Binding Protein 1 (hHint1) Activated ProTides.

Nucleotide analogues that incorporate a metabolically labile nucleoside phosphoramidate (a ProTide) have found utility as prodrugs. In humans, ProTides can be cleaved by human histidine triad nucleotide binding protein 1 (hHint1) to expose the nucleotide monophosphate. Activation by this route circumvents highly selective nucleoside kinases that limit the use of nucleosides as prodrugs.

Inhibition by divalent metal ions of human histidine triad nucleotide binding protein1 (hHint1), a regulator of opioid analgesia and neuropathic pain.

Human histidine triad nucleotide binding protein 1 (hHint1) is a purine nucleoside phosphoramidase and adenylate hydrolase that has emerged as a potential therapeutic target for the management of pain. However, the molecular mechanism of Hint1 in the signaling pathway has remained less clear. The role of metal ions in regulating postsynaptic transmission is well known, and the active site of hHint1 contains multiple histidines.

Caught before Released: Structural Mapping of the Reaction Trajectory for the Sofosbuvir Activating Enzyme, Human Histidine Triad Nucleotide Binding Protein 1 (hHint1).

Human histidine triad nucleotide binding protein 1 (hHint1) is classified as an efficient nucleoside phosphoramidase and acyl-adenosine monophosphate hydrolase. Human Hint1 has been shown to be essential for the metabolic activation of nucleotide antiviral pronucleotides (i.e.

Structure-Based Optimization of Pyridoxal 5'-Phosphate-Dependent Transaminase Enzyme (BioA) Inhibitors that Target Biotin Biosynthesis in Mycobacterium tuberculosis.

The pyridoxal 5'-phosphate (PLP)-dependent transaminase BioA catalyzes the second step in the biosynthesis of biotin in Mycobacterium tuberculosis (Mtb) and is an essential enzyme for bacterial survival and persistence in vivo. A promising BioA inhibitor 6 containing an N-aryl, N'-benzoylpiperazine scaffold was previously identified by target-based whole-cell screening. Here, we explore the structure-activity relationships (SAR) through the design, synthesis, and biological evaluation of a systematic series of analogues of the original hit using a structure-based drug design strategy, which was enabled by cocrystallization of several analogues with BioA.

Rational Optimization of Mechanism-Based Inhibitors through Determination of the Microscopic Rate Constants of Inactivation.

Mechanism-based inhibitors (MBIs) are widely employed in chemistry, biology, and medicine because of their exquisite specificity and sustained duration of inhibition. Optimization of MBIs is complicated because of time-dependent inhibition resulting from multistep inactivation mechanisms. The global kinetic parameters k and K have been used to characterize MBIs, but they provide far less information than is commonly assumed, as shown by derivation and simulation of these parameters.

Design, Synthesis, and Characterization of Sulfamide and Sulfamate Nucleotidomimetic Inhibitors of hHint1.

Hint1 has recently emerged to be an important target of interest due to its involvement in the regulation of a broad range of CNS functions including opioid signaling, tolerance, neuropathic pain, and nicotine dependence. A series of inhibitors were rationally designed, synthesized, and tested for their inhibitory activity against hHint1 using isothermal titration calorimetry (ITC). The studies resulted in the development of the first small-molecule inhibitors of hHint1 with submicromolar binding affinities.

Ligand-induced expansion of the S1' site in the anthrax toxin lethal factor.

The Bacillus anthracis lethal factor (LF) is one component of a tripartite exotoxin partly responsible for persistent anthrax cytotoxicity after initial bacterial infection. Inhibitors of the zinc metalloproteinase have been investigated as potential therapeutic agents, but LF is a challenging target because inhibitors lack sufficient selectivity or possess poor pharmaceutical properties. These structural studies reveal an alternate conformation of the enzyme, induced upon binding of specific inhibitors, that opens a previously unobserved deep pocket termed S1'(∗) which might afford new opportunities to design selective inhibitors that target this subsite.

Probing the S2' Subsite of the Anthrax Toxin Lethal Factor Using Novel N-Alkylated Hydroxamates.

The lethal factor (LF) enzyme secreted by Bacillus anthracis is a zinc hydrolase that is chiefly responsible for anthrax-related cell death. Although many studies of the design of small molecule LF inhibitors have been conducted, no LF inhibitor is yet available as a therapeutic agent. Inhibitors with considerable chemical diversity have been developed and investigated; however, the LF S2' subsite has not yet been systematically explored as a potential target for lead optimization.

Targeting Mycobacterium tuberculosis Biotin Protein Ligase (MtBPL) with Nucleoside-Based Bisubstrate Adenylation Inhibitors.

Mycobacterium tuberculosis (Mtb), responsible for both latent and symptomatic tuberculosis (TB), remains the second leading cause of mortality among infectious diseases worldwide. Mycobacterial biotin protein ligase (MtBPL) is an essential enzyme in Mtb and regulates lipid metabolism through the post-translational biotinylation of acyl coenzyme A carboxylases. We report the synthesis and evaluation of a systematic series of potent nucleoside-based inhibitors of MtBPL that contain modifications to the ribofuranosyl ring of the nucleoside.

Fragment-based exploration of binding site flexibility in Mycobacterium tuberculosis BioA.

The PLP-dependent transaminase (BioA) of Mycobacterium tuberculosis and other pathogens that catalyzes the second step of biotin biosynthesis is a now well-validated target for antibacterial development. Fragment screening by differential scanning fluorimetry has been performed to discover new chemical scaffolds and promote optimization of existing inhibitors. Calorimetry confirms binding of six molecules with high ligand efficiency.

Target-based identification of whole-cell active inhibitors of biotin biosynthesis in Mycobacterium tuberculosis.

Biotin biosynthesis is essential for survival and persistence of Mycobacterium tuberculosis (Mtb) in vivo. The aminotransferase BioA, which catalyzes the antepenultimate step in the biotin pathway, has been established as a promising target due to its vulnerability to chemical inhibition. We performed high-throughput screening (HTS) employing a fluorescence displacement assay and identified a diverse set of potent inhibitors including many diversity-oriented synthesis (DOS) scaffolds.

Anthrax toxin lethal factor domain 3 is highly mobile and responsive to ligand binding.

The secreted anthrax toxin consists of three components: the protective antigen (PA), edema factor (EF) and lethal factor (LF). LF, a zinc metalloproteinase, compromises the host immune system primarily by targeting mitogen-activated protein kinase kinases in macrophages. Peptide substrates and small-molecule inhibitors bind LF in the space between domains 3 and 4 of the hydrolase.

Fragment-based identification of an inducible binding site on cell surface receptor CD44 for the design of protein-carbohydrate interaction inhibitors.

Selective inhibitors of hyaluronan (HA) binding to the cell surface receptor CD44 will have value as probes of CD44-mediated signaling and have potential as therapeutic agents in chronic inflammation, cardiovascular disease, and cancer. Using biophysical binding assays, fragment screening, and crystallographic characterization of complexes with the CD44 HA binding domain, we have discovered an inducible pocket adjacent to the HA binding groove into which small molecules may bind. Iterations of fragment combination and structure-driven design have allowed identification of a series of 1,2,3,4-tetrahydroisoquinolines as the first nonglycosidic inhibitors of the CD44-HA interaction.

Inhibition of Mycobacterium tuberculosis transaminase BioA by aryl hydrazines and hydrazides.

7,8-Diaminopelargonic acid synthase (BioA) of Mycobacterium tuberculosis is a recently validated target for therapeutic intervention in the treatment of tuberculosis (TB). Using biophysical fragment screening and structural characterization of compounds, we have identified a potent aryl hydrazine inhibitor of BioA that reversibly modifies the pyridoxal-5'-phosphate (PLP) cofactor, forming a stable quinonoid. Analogous hydrazides also form covalent adducts that can be observed crystallographically but are incapable of inactivating the enzyme.

Searching for likeness in a database of macromolecular complexes.

A software tool and workflow based on distance geometry is presented that can be used to search for local similarity in substructures in a comprehensive database of experimentally derived macromolecular structure. The method does not rely on fold annotation, specific secondary structure assignments, or sequence homology and may be used to locate compound substructures of multiple segments spanning different macromolecules that share a queried backbone geometry. This generalized substructure searching capability is intended to allow users to play an active part in exploring the role specific substructures play in larger protein domains, quaternary assemblies of proteins, and macromolecular complexes of proteins and polynucleotides.

The structure of the TOG-like domain of Drosophila melanogaster Mast/Orbit.

Mast/Orbit is a nonmotor microtubule-associated protein (MAP) present in Drosophila melanogaster that reportedly binds microtubules at the plus end and is essential for mitosis. Sequence analysis has shown that the N-terminal domain (Mast-M1) resembles TOG domains from the Dis1-TOG family of proteins and stands as a representative of one of the three subclasses of divergent TOG-like domains (TOGL1) that includes human CLASP1. The crystal structure of Mast-M1 has been determined at 2.

Structural characterization of human histidine triad nucleotide-binding protein 2, a member of the histidine triad superfamily.

The histidine triad proteins (HITs) constitute a large and ubiquitous superfamily of nucleotide hydrolases. The human histidine triad nucleotide-binding proteins (hHints) are a distinct class of HITs noted for their acyl-AMP hydrolase and phosphoramidase activity. The first high-resolution crystal structures of hHint2 with and without bound AMP are described.

Use of differential scanning fluorimetry to optimize the purification and crystallization of PLP-dependent enzymes.

Differential scanning fluorimetry (DSF) is a practical and accessible technique that allows the assessment of multiphasic unfolding behavior resulting from subsaturating binding of ligands. Multiphasic unfolding is indicative of a heterogenous protein solution, which frequently interferes with crystallization and complicates functional characterization of proteins of interest. Along with UV-Vis spectroscopy, DSF was used to guide purification and crystallization improvements for the pyridoxal 5'-phosphate (PLP) dependent transaminase BioA from Mycobacterium tuberculosis.

Discovery of a series of 2-(1H-pyrazol-1-yl)pyridines as ALK5 inhibitors with potential utility in the prevention of dermal scarring.

A series of 2-(1H-pyrazol-1-yl)pyridines are described as inhibitors of ALK5 (TGFβ receptor I kinase). Modeling compounds in the ALK5 kinase domain enabled some optimization of potency via substitutions on the pyrazole core. One of these compounds PF-03671148 gave a dose dependent reduction in TGFβ induced fibrotic gene expression in human fibroblasts.