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Identification of the Abl- and rasGAP-associated 62 kDa protein as a docking protein, Dok.

A 62 kDa protein is highly phosphorylated in many cells containing activated tyrosine kinases. This protein, characterized mainly by its avid association with rasGAP, has proved elusive. Anti-phosphotyrosine antibody was used to purify p62. From peptide sequence, molecular cloning revealed a cDNA encoding a novel protein, p62dok, with little homology to others but with a prominent set of tyrosines and nearby sequences suggestive of SH2 binding sites. In cells, v-Abl tyrosine kinase binds and strongly phosphorylates p62dok, which then binds rasGAP. A monoclonal antibody, 2C4, to the rasGAP-associated p62 reacts with p62dok. Thus, p62dok appears to be the long-sought major substrate of many tyrosine kinases.

Amino Acid Sequence↗

viwish: a visualization server for protein modelling and docking.

A visualization tool viwish for proteins based on the Tcl command language has been developed. The system is completely menu driven and can display arbitrary many proteins in arbitrary many windows. It isinstantly t o use, even for non computer experts and provides possibilities to modify menus, configurations, and windows. It may be used as a stand-alone molecular graphics package or as a graphics server for external programs. Communications with these client applications is established even across different machines (through the send command to Tk, an extension of Tcl). In addition, a wide rage of chemical data like molecular surfaces and 3D gridded samplings of chemical features can be displayed. Therefore the systmen is especially useful for the development of algorithms that need visual distributed freely, including the source code.

Binding Sites↗

The mammalian ShcB and ShcC phosphotyrosine docking proteins function in the maturation of sensory and sympathetic neurons.

Shc proteins possess SH2 and PTB domains and serve a scaffolding function in signaling by a variety of receptor tyrosine kinases. There are three known mammalian Shc genes, of which ShcB and ShcC are primarily expressed in the nervous system. We have generated null mutations in ShcB and ShcC and have obtained mice lacking either ShcB or ShcC or both gene products. ShcB-deficient animals exhibit a loss of peptidergic and nonpeptidergic nociceptive sensory neurons, which is not enhanced by additional loss of ShcC. Mice lacking both ShcB and ShcC exhibit a significant loss of neurons within the superior cervical ganglia, which is not observed in either mutant alone. The results indicate that these Shc family members possess both unique and overlapping functions in regulating neural development and suggest physiological roles for ShcB/ShcC in TrkA signaling.

Adaptor Proteins, Signal Transducing↗

Synaptic vesicle docking and fusion.

Neurotransmitter secretion shares many features with constitutive membrane trafficking. In both cases, vesicles are targeted to a specific acceptor membrane and fuse via a series of protein-protein interactions. Recent work has added to the list of protein complexes involved and is beginning to define the order in which they act. The rapid fusion, precise regulation and plasticity characteristic of synaptic exocytosis probably results from the addition of specialized regulators.

Animals↗

Immune signalling: SHP-2 docks at multiple ports.

The protein tyrosine phosphatase SHP-2 functions in many diverse signalling pathways. The recent identification of a SHP-2-binding protein as a homologue of the Grb2-associated adaptor protein Gab1 sheds light on the role of SHP-2 in immune signalling.

Animals↗

Ligand recognition in mu opioid receptor: experimentally based modeling of mu opioid receptor binding sites and their testing by ligand docking.

For three-dimensional understanding of the mechanisms that control potency and selectivity of the ligand binding at the atomic level, we have analysed opioid receptor-ligand interaction based on the receptor's 3D model. As a first step, we have constructed molecular models for the multiple opioid receptor subtypes using bacteriorhodopsin as a template. The S-activated dihydromorphine derivatives should serve as powerful tools in mapping the three-dimensional structure of the mu opioid receptor, including the nature of the agonist-mediated conformational change that permits G protein-coupling to "second messenger' effector molecules, and in identifying specific ligand-binding contacts with the mu opioid receptor. The analyses of the interactions of some opioid ligands with the predicted ligand binding sites are consistent with the results of the affinity labeling experiments.

Affinity Labels↗

Docking study of enantiomeric fonofos oxon bound to the active site of Torpedo californica acetylcholinesterase.

Molecular interaction between enantiomeric fonofos oxon (O-ethyl S-phenyl ethylphosphonothiolate) and acetylcholinesterase (AChE) of Torpedo californica was evaluated by using the Cerius2 program. It was suggested that the difference in the inhibitory activity of the two enantiomers of fonofos oxon on AChE is due to the steric hindrance in binding to the AChE active site.

Acetylcholinesterase↗

Crystal structure of paromomycin docked into the eubacterial ribosomal decoding A site.

BACKGROUND: Aminoglycoside antibiotics interfere with translation in both gram-positive and gram-negative bacteria by binding to the tRNA decoding A site of the 16S ribosomal RNA. RESULTS: Crystals of complexes between oligoribonucleotides incorporating the sequence of the ribosomal A site of Escherichia coli and the aminoglycoside paromomycin have been solved at 2.5 A resolution. Each RNA fragment contains two A sites inserted between Watson-Crick pairs. The paromomycin molecules interact in an enlarged deep groove created by two bulging and one unpaired adenines. In both sites, hydroxyl and ammonium side chains of the antibiotic form 13 direct hydrogen bonds to bases and backbone atoms of the A site. In the best-defined site, 8 water molecules mediate 12 other hydrogen bonds between the RNA and the antibiotics. Ring I of paromomycin stacks over base G1491 and forms pseudo-Watson-Crick contacts with A1408. Both the hydroxyl group and one ammonium group of ring II form direct and water-mediated hydrogen bonds to the U1495oU1406 pair. The bulging conformation of the two adenines A1492 and A1493 is stabilized by hydrogen bonds between phosphate oxygens and atoms of rings I and II. The hydrophilic sites of the bulging A1492 and A1493 contact the shallow groove of G=C pairs in a symmetrical complex. CONCLUSIONS: Water molecules participate in the binding specificity by exploiting the antibiotic hydration shell and the typical RNA water hydration patterns. The observed contacts rationalize the protection, mutation, and resistance data. The crystal packing mimics the intermolecular contacts induced by aminoglycoside binding in the ribosome.

Amino Acid Motifs↗

A core-weighted fitting method for docking atomic structures into low-resolution maps: application to cryo-electron microscopy.

Cryo-electron microscopy of "single particles" is a powerful method to analyze structures of large macromolecular assemblies that are not amenable to investigation by traditional X-ray crystallographic methods. A key step in these studies is to obtain atomic interpretations of multiprotein complexes by fitting atomic structures of individual components into maps obtained from electron microscopic data. Here, we report the use of a "core-weighting" method, combined with a grid-threading Monte Carlo (GTMC) approach for this purpose. The "core" of an individual structure is defined to represent the part where the density distribution is least likely to be altered by other components that comprise the macromolecular assembly of interest. The performance of the method has been evaluated by its ability to determine the correct fit of (i) the alpha-chain of the T-cell receptor variable domain into a simulated map of the alphabeta complex at resolutions between 5 and 40 A, and (ii) the E2 catalytic domain of the pyruvate dehydrogenase into an experimentally determined map, at 14 A resolution, of the icosahedral complex formed by 60 copies of this enzyme. Using the X-ray structures of the two test cases as references, we demonstrate that, in contrast to more traditional methods, the combination of the core-weighting method and the grid-threading Monte Carlo approach can identify the correct fit reliably and rapidly from the low-resolution maps that are typical of structures determined with the use of single-particle electron microscopy.

Animals↗

Approaches to solving the rigid receptor problem by identifying a minimal set of flexible residues during ligand docking.

BACKGROUND: Using fixed receptor sites derived from high-resolution crystal structures in structure-based drug design does not properly account for ligand-induced enzyme conformational change and imparts a bias into the discovery and design of novel ligands. We sought to facilitate the design of improved drug leads by defining residues most likely to change conformation, and then defining a minimal manifold of possible conformations of a target site for drug design based on a small number of identified flexible residues. RESULTS: The crystal structure of thymidylate synthase from an important pathogenic target Pneumocystis carinii (PcTS) bound to its substrate and the inhibitor, BW1843U89, is reported here and reveals a new conformation with respect to the structure of PcTS bound to substrate and the more conventional antifolate inhibitor, CB3717. We developed an algorithm for determining which residues provide 'soft spots' in the protein, regions where conformational adaptation suggests possible modifications for a drug lead that may yield higher affinity. Remodeling the active site of thymidylate synthase with new conformations for only three residues that were identified with this algorithm yields scores for ligands that are compatible with experimental kinetic data. CONCLUSIONS: Based on the examination of many protein/ligand complexes, we develop an algorithm (SOFTSPOTS) for identifying regions of a protein target that are more likely to accommodate plastically to regions of a drug molecule. Using these indicators we develop a second algorithm (PLASTIC) that provides a minimal manifold of possible conformations of a protein target for drug design, reducing the bias in structure-based drug design imparted by structures of enzymes co-crystallized with inhibitors.

Algorithms↗

A correlation between TCR Valpha docking on MHC and CD8 dependence: implications for T cell selection.

T cell receptors (TCR) adopt a similar orientation when binding with major histocompatibility complex (MHC) molecules, yet the biological mechanism that generates this similar TCR orientation remains obscure. We show here the cocrystallographic structure of a mouse TCR bound to a human MHC molecule not seen by the TCR during thymic development. The orientation of this xenoreactive murine TCR atop human MHC deviates from the typical orientation more than any previously determined TCR/MHC structure. This unique orientation is solely due to the placement of the TCR Valpha domain on the MHC. In light of new information provided by this structure, we have reanalyzed the existing TCR/MHC cocrystal structures and discovered unique features of TCR Valpha domain position on class I MHC that correlate with CD8 dependence. Finally, we propose that the orientation seen in TCR recognition of MHC is a consequence of selection during T cell development.

Animals↗

Human type 10 17 beta-hydroxysteroid dehydrogenase: molecular modelling and substrate docking.

17 beta-hydroxysteroid dehydrogenases catalyze the oxidoreduction of hydroxy/oxo groups at position C17 of steroid hormones, thereby constituting a prereceptor control mechanism of hormone action. At present, 11 different mammalian 17 beta-hydroxysteroid dehydrogenases have been identified, catalyzing the cell- and steroid-specific activation and inactivation of estrogens and androgens. The human type 10 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD-10) is a multifunctional mitochondrial enzyme that efficiently catalyzes the oxidative inactivation at C17 of androgens and estrogens. However, it also mediates oxidation of 3 alpha-hydroxy groups of androgens, thereby reactivating androgen metabolites. Finally, it is involved in beta-oxidation of fatty acids by catalyzing the L-hydroxyacyl CoA dehydrogenase reaction of the beta-oxidation cycle. These features and expression profiles suggest a critical role of 17 beta-HSD-10 in neurodegenerative and steroid-dependent cancer forms. Since no three-dimensional structure of 17 beta-HSD-10 is available, homology modelling was carried out to understand the molecular basis of these substrate specificities. The structure obtained displays the properties of a one-domain, alpha/beta fold enzyme of the SDR family. The active site is located within a large, hydrophobic cleft, which forms optimal contacts with the different steroid surfaces. The data provide explanations for the substrate specificities toward the various classes of sex steroid hormones. The model is suitable to explore substrate and inhibitor characteristics that may be used in the development of novel strategies in the treatment of degenerative or malignant diseases.

17-Hydroxysteroid Dehydrogenases↗