ABSTRACT
Engineered cytochromeâ P450 monooxygenase variants are reported as highly active and selective catalysts for the bioorthogonal uncaging of propargylic and benzylic ether protected substrates, including uncaging in living E. coli. observed selectivity is supported by induced-fit docking and molecular dynamics simulations. This proof-of-principle study points towards the utility of bioorthogonal enzyme/protecting group pairs for applications in the life sciences.
Subject(s)
Cytochrome P-450 Enzyme System/metabolism , Escherichia coli/metabolism , Alcohols/chemistry , Alcohols/metabolism , Cytochrome P-450 Enzyme System/chemistry , Enzyme Activation , Escherichia coli/cytology , Ethers/chemistry , Ethers/metabolism , Models, Molecular , Molecular Structure , Protein EngineeringABSTRACT
The probe-based discovery of the first small-molecule inhibitor of the repair enzyme 8-oxo-dGTPase (MTH1) is presented, which is an unconventional cyclometalated ruthenium half-sandwich complex. The organometallic inhibitor with low-nanomolar activity displays astonishing specificity, as verified in tests with an extended panel of protein kinases and other ATP binding proteins. The binding of the organometallic inhibitor to MTH1 is investigated by protein crystallography.
Subject(s)
DNA Repair Enzymes/chemistry , Phosphoric Monoester Hydrolases/chemistry , Ruthenium/chemistry , DNA Repair Enzymes/pharmacology , Humans , Organometallic Compounds/chemistry , Organometallic Compounds/pharmacology , Phosphoric Monoester Hydrolases/pharmacologyABSTRACT
The regioselective cyclometalation of 4-(pyridin-2-yl)phthalimide was exploited for the economical design of organometallic protein kinase inhibitors. 4-(Pyridin-2-yl)phthalimide can be prepared from inexpensive 4-bromophthalimide in just three steps including one Pd-catalyzed Stille cross-coupling. The versatility of this new ligand was demonstrated with the synthesis of ruthenium(II) half-sandwich as well as octahedral ruthenium(II) and iridium(III) complexes. The regioselectivity of the C-H activation in the course of the cyclometalation can be influenced by the reaction conditions and the steric demand of the introduced metal complex fragment. The biological activity of this new class of metalated phthalimides was evaluated by profiling two representative members against a large panel of human protein kinases. A cocrystal structure of one metallo-phthalimide with the protein kinase Pim1 confirmed an ATP-competitive binding with the intended hydrogen bonding between the phthalimide moiety and the hinge region of the ATP-binding site.
Subject(s)
Coordination Complexes/chemistry , Metals/chemistry , Phthalimides/chemistry , Protein Kinase Inhibitors/chemistry , Coordination Complexes/pharmacology , Humans , Metals/pharmacology , Phthalimides/pharmacology , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins c-pim-1/antagonists & inhibitorsABSTRACT
The generation of synthetic compounds with exclusive target specificity is an extraordinary challenge of molecular recognition and demands novel design strategies, in particular for large and homologous protein families such as protein kinases with more than 500 members. Simple organic molecules often do not reach the necessary sophistication to fulfill this task. Here, we present six carefully tailored, stable metal-containing compounds in which unique and defined molecular geometries with natural-product-like structural complexity are constructed around octahedral ruthenium(II) or iridium(III) metal centers. Each of the six reported metal compounds displays high selectivity for an individual protein kinase, namely GSK3α, PAK1, PIM1, DAPK1, MLCK, and FLT4. Although being conventional ATP-competitive inhibitors, the combination of the unusual globular shape and rigidity characteristics, of these compounds facilitates the design of highly selective protein kinase inhibitors. Unique structural features of the octahedral coordination geometry allow novel interactions with the glycine-rich loop, which contribute significantly to binding potencies and selectivities. The sensitive correlation between metal coordination sphere and inhibition properties suggests that in this design, the metal is located at a "hot spot" within the ATP binding pocket, not too close to the hinge region where globular space is unavailable, and at the same time not too far out toward the solvent where the octahedral coordination sphere would not have a significant impact on potency and selectivity. This study thus demonstrates that inert (stable) octahedral metal complexes are sophisticated structural scaffolds for the design of highly selective chemical probes.
Subject(s)
Coordination Complexes/chemistry , Coordination Complexes/pharmacology , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Protein Kinases/metabolism , Binding Sites , Crystallography, X-Ray , Humans , Iridium/chemistry , Iridium/pharmacology , Models, Molecular , Protein Binding , Protein Kinases/chemistry , Ruthenium Compounds/chemistry , Ruthenium Compounds/pharmacology , Structure-Activity RelationshipABSTRACT
Screening of a library of structurally unusual osmacyclic complexes for their antiproliferate properties in HeLa cells led to the discovery of a highly cytotoxic eta2-allene osmacycle. In this remarkably stable complex, osmium constitutes part of a metallacycle through the formation of a sigma-bond to a carbon in combination with coordination to an allene moiety. The osmacycle strongly induces apoptosis in Burkitt-like lymphoma cells at submicromolar concentrations. The reduction of the mitochondrial membrane potential, the induction of DNA fragmentation, and the activation of caspases-9 and -3 reveal that programmed cell death occurs through the intrinsic mitochondrial pathway. From the lipophilic and cationic nature of the osmacycle, in addition to a low oxidation potential (E1/2=+0.27 V vs. Fc/Fc+, Fc=ferrocene) it is proposed that mitochondria are the cellular target where oxidative decomposition initiates apoptosis.
