WILBERT

Wildauer Bücher+E-Medien Recherche-Tool

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 97 (1975), S. 1973-1974 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: ribonuclease ; sequence alignment ; enzyme specificity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The P-30 protein (Onconase™)Onconase™ is a trademark of Alfacell Corporation. of Rana pipiens oocytes and early embryos is homologous to members of the pancreatic ribonuclease superfamily and exhibits an antitumor activity in vitro and in vivo. It appears that the ribonucleolytic activity of P-30 protein may be required for its antitumor effects. A comparative molecular model of P-30 protein has been constructed based upon the known three-dimensional structure of bovine pancreatic RNase A in order to provide structural information. Functionally, these enzymes hydrolyze oligoribonucleotides to pyrimidine-3′-phosphate monoesters and 5′-OH ribonucleotides. In the modeling procedure, automated sequence alignments were revised based upon the inspection of the RNase A structure before the amino acids of the P-30 protein were assigned the coordinates of the RNase A template. The inevitable intermolecular steric clashes that result were relieved on an interactive graphics device through theadjustment of side chain torsion angles. This process was followed by energy minimization of the model, which served to optimize stereochemical geometry and to relieve any remaining unacceptably close contacts. The resulting model retains the essential features of RNase A as sequence insertions and deletions are almost exclusively found in exposed surface loops. The all atom superposition of active site residues of the P-30 protein model and an identically minimized RNase A structure has a root mean square deviation of 0.52 Å. Though tentative, the model is consistent with a pyrimidine specificity. Further, the model suggests Lys9 (P-30 protein) can donate a hydrogen bond to the active site phosphate, whereas it is unlikely that P-30 protein binds the 3′-ribonucleotide in a fashion similar to RNase A. P-30 protein has been crystallized in an orthorhombic space group, P212121, with unit cell dimensions, a = 40.76, b = 69.77, and c = 32.54 Aring;. The crystals grow as small rosettes from an ammonium sulfate solution at pH 4.5. © 1992 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: computer modeling ; trifluoperazine ; conformational change ; calcium binding proteins ; hydrophobic binding interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Among the known regulatory proteins that are conformationally sensitive to the binding of calcium ions, calmodulin and troponin-C have the greatest primary sequence homology. This observation has led to the conclusion that the most accurate predicted molecular model of calmodulin would be based on the X-ray crystallographic coordinates of the highly refined structure of turkey skeletal troponin-C. This paper describes the structure of calmodulin built from such a premise. The resulting molecular model was subjected to conjugate gradient energy minimization to remove unacceptable intramolecular non-bonded contacts. In the analysis of the resulting structure, many features of calmodulin, including the detailed conformation of the Ca2+-binding loops, the amino- and carboxy-terminal hydrophobic patches of the Ca2+-bound form, and the several clusters of acidic residues can be reconciled with much of the previously published solution data. Calmodulin in missing the N-terminal helix characteristic of troponin-C. The deletion of three residues from the central helical linker (denoted D/E in troponin-D) shortens the molecule and changes the orientation of the two domains of calmodulin by 60° relative to those in troponin-C. The molecular model has been used to derive two possible binding sites for the antipsychotic drug trifluoperazine, a potent competitive inhibitor of calmodulin activity.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: computer graphics ; energy minimization ; proteolytic enzymes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Two genes that are expressed when precursor cytotoxic T lymphocytes are transformed to T killer cells have been cloned and sequenced. The derived amino acid sequences, coding for the cytotoxic cell protease 1 (CCP1) and Hannuka factor (HF) are highly homologous to members of the serine proteinase family. Comparative molecular model building using the known three-dimensional structures and the derived amino acid sequences of the lymphocyte enzymes has been provided useful information, especially in predicting the conformations of the substrate binding sites. In applying this modelling procedure, we used the X-ray structures of four serine proteinase to provide a structurally based sequences alignment: α-chymotrypsin (CHT), bovine trypsin (BT), Streptomyces griseus trypsin (SGT), and rat must cell protease 2 (RMCP2). The root mean square differences in α-carbon atom positions among these four structures when compared in a pairwise fashions range form 0.79 to 0.97 Å for structurally equivalent residues. Te sequences of the two lymphocyte enzymes were then aligned to these proteinase using chemical criteria and the superimposed X-ray structures as guides. The alignment showed that the sequence of CCP1 was most similar to RMCP2, whereas HF has regions of homology with both RMCP2 and BT. RmCP2 and BT as templates for HF, the molecular models were constructed. Intermolecular steric clashes that resulted from replacement of amino acid chains of the templates by the aligned residues of CCP1 and HF were relieved by adjustment of the side chain conformational angels in an interactive computer graphics device. This process was followed by energy minimization of the enzyme model to optimize the stereochemical geometry and to relieve any remaining unacceptably close nonbonded contacts. The resulting model of CCP1 has an arginie residue at position 226 in the specificity pocket, thereby predicting a substrate preference for P1 aspartate or glutamate residues. The model also predicts favorable binding for a small hydrophobic residue at the P2 position of the substrate. The primary specificity pocket of HF resembles that of BT and therefore predicts a lysine or arginine preference for the P1 residue. The arginine at position 99 in the model of HF suggests a preference for aspartate or glutamate side chains in the P2 positions of the substrate. Both CCP1 and HF have a free cysteine in the segment of the polypeptide 88 to 93. Models of the dimeric form of these enzymes can be constructed by forming disulfide bridges between the suitably oriented monomers, ie., Cys88-Cys88′ for CCP1 and Cys93-Cys93′ for HF.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: signal peptidase ; crystals ; X-ray analysis ; detergent ; soluble fragment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Leader peptidase, a novel serine protease in Escherichia coli, catalyzes the cleavage of the amino-terminal leader sequences from exported proteins. It is an integral membrane protein containing two transmembrane segments with its carboxy-terminal catalytic domain residing in the periplasmic space. Here, we report a procedure for the purification and the crystallization of a soluble non-membrane-bound form of leader peptidase (Δ2-75). Crystals were obtained by the sitting-drop vapor diffusion technique using ammonium dihydrogen phosphate as the precipitant. Interestingly, we have found that the presence of the detergent Triton X-100 is required to obtain crystals sufficiently large for X-ray analysis. The crystals belong to the tetragonal space group P42212, with unit cell dimensions of a = b = 115 Å and c = 100 Å, and contain 2 molecules per asymmetric unit. This is the first report of the crystallization of a leader (or signal) peptidase. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: calcium ; plant ; environmental stress ; TCH genes ; signal transduction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Plants adapt to various stresses by developmental alterations that render them less easily damaged. Expression of the TCH2 gene of Arabidopsis is strongly induced by stimuli such as touch and wind. The gene product, TCH2, belongs to the calmodulin (CaM) family of proteins and contains four highly conserved Ca2+-binding EF-hands. We describe here the structure of TCH2 in the fully Ca2+-saturated form, constructed using comparative molecular modeling, based on the x-ray structure of paramecium CaM. Like known CaMs, the overall structure consists of two globular domains separated by a linker helix. However, the linker region has added flexibility due to the presence of 5 glycines within a span of 6 residues. In addition, TCH2 is enriched in Lys and Arg residues relative to other CaMs, suggesting a preference for targets which are more negatively charged. Finally, a pair of Cys residues in the C-terminal domain, Cys126 and Cys131, are sufficiently close in space to form a disulfide bridge. These predictions serve to direct future biochemical and structural studies with the overall aim of understanding the role of TCH2 in the cellular response of Arabidopsis to environmental stimuli. Proteins 27:144-153 © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: computer modelling ; Ca2+-binding proteins ; hydrophobic binding interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Crystals of troponin are stabilized by an intermolecular interaction that involves the packing of helix A from the N-terminal domain of one molecule onto the exposed hydrophobic cleft of the C-terminal domain of a symmetry related molecules. Analysis of this molecular recognition interaction in troponin C suggests a possible mode for the binding of amphiphilic helical molecules to troponin C and to calmodulin. From the template provided by this troponin C packing, it has been possible to build a model of the contact region of mastoporan as it might be bound to the two Ca2+ binding proteins. A possible binding mode of melittin to calmodulin is also proposed. Although some of the characteristics of binding are similar for the two amphiphilic peptides, the increased length of melittin requires a significant bend in the calmodulin central helix similar to that suggested recently for the myosin light chain kinase calmodulin binding peptide (Persechini and Kretsinger: Journal of Cardiovascular Pharmacology 12:501-512, 1988). Not only are the hydrophobic interactions important in this model, but there are several favorable electrostatic interactions that are predicted as a result of the molecular modeling. The regions of troponin-C and calmodulin to which amphiphilic helices bind are similar to the regions to which the neuroleptic drugs such as trifluoperazine have been predicted to bind (Strynadka and James: Proteins 3:1-17, 1988).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: molecular model ; comparative model ; homology model ; structure prediction ; calculated structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In spite of the tremendous increase in the rate at which protein structures are being determined, there is still an enormous gap between the numbers of known DNA-derived sequences and the numbers of three-dimensional structures. In order to shed light on the biological functions of the molecules, researchers often resort to comparative molecular modeling. Earlier work has shown that when the sequence alignment is in error, then the comparative model is guaranteed to be wrong. In addition, loops, the sites of insertions and deletions in families of homologous proteins, are exceedingly difficult to model. Thus, many of the current problems in comparative molecular modeling are minor versions of the global protein folding problem. In order to assess objectively the current state of comparative molecular modeling, 13 groups submitted blind predictions of seven different proteins of undisclosed tertiary structure. This assessment shows that where sequence identity between the target and the template structure is high (〉 70%), comparative molecular modeling is highly successful. On the other hand, automated modeling techniques and sophisticated energy minimization methods fail to improve upon the starting structures when the sequence identity is low (∼30%). Based on these results it appears that insertions and deletions are still major problems. Successfully deducing the correct sequence alignment when the local similarity is low is still difficult. We suggest some minimal testing of submitted coordinates that should be required of authors before papers on comparative molecular modeling are accepted for publication in journals. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: bacterial lactate dehydrogenase ; X-ray crystallography ; site-directed mutation ; stereospecificity ; image plates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Bacillus stearothermophilus lactate dehydrogenase, one of the most thermostable bacterial enzymes known, has had its three-dimensional structure solved, the gene coding for it has been cloned, and the proteincan be readily overexpressed. Two mutants of the enzyme have been prepared. In one, Arg171 was changed to Trp (R171W) and Gln102 was changed to Arg (Q102R). In the other, the mutation Q102R was maintained, but Arg171 was changed to Tyr (R171Y). In addition, an inadvertent C97G mutant was present. Both mutants have been crystallized by the hanging drop vapor diffusion method at room temperature. Bipyrimidal crystals have been obtained against (NH4)2SO4in 50 mM piperazine HCI buffer. The crystals belong to space group P6622 (P6622) (whereas the native enzyme, the structure of which has been solved by Piontek et al., Proteins 7:74-92, 1990) crystallized in the space group (P61) with a = 102.3 Å, c = 168.6 Å for the R171W, Q102R, C97G triple mutant, and a = 98.2 Å; c = 162.1 Å for the R171Y, Q102R, C97G mutant. These crystal forms appear to contain one-quarter of a tetramer (Mr 135,000)in the asymmetric unit and have (VM values of 3.8 and 3.3 Å3/dalton, respectively). The R171W mutant diffracts to 2.5 Å and the R171Y mutant to approximately 3.5 Å © 1992 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 369 (1994), S. 72-76 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] For crystallographic work we used a double mutant form of HAV-3C in which the two cysteine residues were replaced by site-directed mutagenesis (at residue 24 (Cys 24 Ser) and at residue 172 in the active site (Cys 172 Ala))9. The HAV-3C model has now been refined to a present -factor of 20.9% ...
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...