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[Image: see text] Small molecule ligand binding to the ATAD2 bromodomain is investigated here through the synergistic combination of molecular dynamics and protein crystallography. A previously unexplored conformation of the binding pocket upon rearrangement of the gatekeeper residue Ile1074 has been found. Further, our investigations reveal how minor structural differences in the ligands result in binding with different plasticity of the ZA loop for this difficult-to-drug bromodomain.

Cytochrome P450 3A4 (CYP3A4) is the major human P450 responsible for the metabolism of carbamazepine (CBZ). To explore the mechanisms of interactions of CYP3A4 with this anticonvulsive drug, we carried out multiple molecular dynamics (MD) simulations, starting with the complex of CYP3A4 manually docked with CBZ. On the basis of these simulations, we engineered CYP3A4 mutants I369F, I369L, A370V, and A370L, in which the productive binding orientation was expected to be stabilized, thus leading to increased turnover of CBZ to the 10,11-epoxide product. In addition, we generated CYP3A4 mutant S119A as a control construct with putative destabilization of the productive binding pose. Evaluation of the kinetics profiles of CBZ epoxidation demonstrate that CYP3A4-containing bacterial membranes (bactosomes) as well as purified CYP3A4 (wild-type and mutants I369L/F) exhibit substrate inhibition in reconstituted systems. In contrast, mutants S119A and A370V/L exhibit S-shaped profiles that are indicative of homotropic cooperativity. MD simulations with two to four CBZ molecules provide evidence that the substrate-binding pocket of CYP3A4 can accommodate more than one molecule of CBZ. Analysis of the kinetics profiles of CBZ metabolism with a model that combines the formalism of the Hill equation with an allowance for substrate inhibition demonstrates that the mechanism of interactions of CBZ with CYP3A4 involves multiple substrate-binding events (most likely three). Despite the retention of the multisite binding mechanism in the mutants, functional manifestations reveal an exquisite sensitivity to even minor structural changes in the binding pocket that are introduced by conservative substitutions such as I369F, I369L, and A370V., Biochemistry, 54 (3), ISSN:0006-2960, ISSN:1520-4995

High throughput docking (HTD) using high performance computing platforms is a multidisciplinary challenge. To handle HTD data effectively and efficiently, we have developed a distributed virtual screening data management system (DVSDMS) in which the data handling and the distribution of jobs are realized by the open-source structured query language database software MySQL. The essential concept of DVSDMS is the separation of the data management from the docking and ranking applications. DVSDMS can be used to dock millions of molecules effectively, monitor the process in real time, analyze docking results promptly, and process up to 10(8) poses by energy ranking techniques. In an HTD campaign to identify kinase inhibitors a low cost Linux PC has allowed DVSDMS to efficiently assign the workload to more than 500 computing clients. Notably, in a stress test of DVSDMS that emulated a large number of clients, about 60 molecules per second were distributed to the clients for docking, which indicates that DVSDMS can run efficiently on very large compute cluster (up to about 40000 cores).

GANDI (Genetic Algorithm-based de Novo Design of Inhibitors) is a computational tool for automatic fragment-based design of molecules within a protein binding site of known structure. A genetic algorithm and a tabu search act in concert to join predocked fragments with a user-supplied list of fragments. A novel feature of GANDI is the simultaneous optimization of force field energy and a term enforcing 2D-similarity to known inhibitor(s) or 3D-overlap to known binding mode(s). Scaffold hopping can be promoted by tuning the relative weights of these terms. The performance of GANDI is tested on cyclin-dependent kinase 2 (CDK2) using a library of about 14 000 fragments and the binding mode of a known oxindole inhibitor to bias the design. Top ranking GANDI molecules are involved in one to three hydrogen bonds with the backbone polar groups in the hinge region of CDK2, an interaction pattern observed in potent kinase inhibitors. Notably, a GANDI molecule with very favorable predicted binding affinity shares a 2-N-phenyl-1,3-thiazole-2,4-diamine moiety with a known nanomolar inhibitor of CDK2. Importantly, molecules with a favorable GANDI score are synthetic accessible. In fact, eight of the 1809 molecules designed by GANDI for CDK2 are found in the ZINC database of commercially available compounds which also contains about 600 compounds with identical scaffolds as those in the top ranking GANDI molecules.

The tyrosine kinase EphB4 is an attractive target for drug design because of its recognized role in cancer-related angiogenesis. Recently, a series of commercially available xanthine derivatives were identified as micromolar inhibitors of EphB4 by high-throughput fragment-based docking into the ATP-binding site of the kinase domain. Here, we have exploited the binding mode obtained by automatic docking for the optimization of these EphB4 inhibitors by chemical synthesis. Addition of only two heavy atoms, methyl and hydroxyl groups, to compound 4 has yielded the single-digit nanomolar inhibitor 66, with a remarkable improvement of the ligand efficiency from 0.26 to 0.37 kcal/(mol per non-hydrogen atom). Compound 66 shows very high affinity for a few other tyrosine kinases with threonine as gatekeeper residue (Abl, Lck, and Src). On the other hand, it is selective against kinases with a larger gatekeeper. A 45 ns molecular dynamics (MD) simulation of the complex of EphB4 and compound 66 provides further validation of the binding mode obtained by fragment-based docking.