ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 391-397 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work we describe calcium binding to two synthetic 34-residue peptides, determined by 1H-nmr spectroscopy. The peptides investigated, SCIII and SCIV, encompass the calcium-binding sites III and IV, respectively, of troponin-C. In the absence of calcium it has previously been shown that each of these peptides possesses little regular secondary structure. Further, the 1H-nmr spectra of an equimolar mixture of both of these apo-peptides (apo-SCIII/SCIV) shows that little interaction occurs between peptides. Upon calcium binding the spectral changes that occur to SCIII/SCIV are consistent with global conformational changes in both peptides. We have shown previously that these conformational changes are a product of calcium binding to SCIII and SCIV to form a two-site heterodimer Ca2-SCIII/SCIV. It is proposed that this calcium-induced folding proceeds via calcium binding to SCIII to form Ca-SCIII, peptide association with apo-SCIV to form the heterodimer Ca-SCIII/SCIV, and calcium binding to form Ca2-SCIII/SCIV. The dissociation constants involved in this pathway, K1, Kd, and K2, respectively, have been determined by stoichiometric calcium titration of SCIII/SCIV, monitored by 1H-nmr spectroscopy. Using this procedure it has been determined that K1 = 3 μM, Kd = 10 μM, and K2 = 2 μM.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 43 (1997), S. 339-366 
    ISSN: 0006-3525
    Keywords: growth factor receptors ; tyrosine kinase ; transforming growth factor - α ; epidermal growth factor ; neurotrophin ; nerve growth factor ; insulin growth factor ; insulin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The focus of this review is the relationship between the three-dimensional structure of ligands of the various members of the growth factor receptor tyrosine kinase superfamily and their interaction with the cognate receptor. Particular attention is given to the transforming growth factor - α, epidermal growth factor (EGF); nerve growth factor, neurotrophin; and insulin-like growth factor - 1 (IGF-1), insulin systems since these have been extensively studied in recent years. The three receptor types, which bind these ligands, are the epidermal growth factor receptor family (erb B receptors), the neurotrophin or Trk receptor family, and IGF-1/insulin receptors, respectively, and represent three distinct members of the tyrosine kinase superfamily. For each of these, formation of the ligand-receptor complex initiates the signal transduction cascade through autophosphorylation by the intracellular tyrosine kinase domain. The extracellular portion of the receptor that contains the ligand binding domain in these systems varies significantly in organization in each case. For the EGF receptor system, ligand binding induces homo- and heterodimerization of the receptor leading to activation of the intracellular kinase. For the Trk receptor system, homodimerization of receptors has been shown to occur, although a second receptor, p75, is also required for high affinity binding of neurotrophins and for enhanced sensitivity of tyrosine kinase activation at low ligand concentrations. The IGF-1 and insulin receptors exist as covalent cross-linked dimers where each monomer is composed of two subunits.The aim of this review is also to discuss the mechanism of ligand-receptor interaction for each of these cases; however, since no structural information is yet available for the ligand-receptor complex, the discussion will largely be centered on the molecular requirements of ligand binding. As these receptors are activated through the ligand binding site on the extracellular domain, this represents a possible target for pharmacological intervention by inhibition or stimulation of this portion of the receptor. Thus from a drug design perspective, the focus of this review is to discuss progress in the development of agonists or antagonists of the ligand for these receptors. © 1998 John Wiley & Sons, Inc. Biopoly 43: 339-366, 1997
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The basic structural organization of striated muscle tissue consists of two types of filaments - thick and thin - which are interdigitated and slide past one another when muscle contracts. In the thick filaments the long matchsticklike myosin molecules are organized into a biopolar structure in which the tails form the core of the filament and the heads project out at both ends. The ATPase activity and acitin-binding properties are located in the projecting heads. It is the interaction of these heads with the thin filaments and the concomitant hydrolysis of ATP that provides the driving force for the sliding of thin over thick filaments. The core of the thin-filament structure is made up of a long double-stranded helical assembly of globular (G) acting monomers known as “F-actin.” Located in each of the two grooves of the F-actin structure is a filament of rodlike tropomyosin molecules aggregated head to tail and spanning the length of the thin filament. Each tropomyosin molecule spans seven G-actin monomers on each of the two strands of F-actin and interacts with one troponin complex. The latter consists of three proteins: troponin-C (TN-C), which binds calcium; troponin-I (TN-I), the inhibitory protein; and troponin-T (TN-T), which binds the troponin complex to tropomyosin. When a nerve impulse stimulates a muscle to contract there is an increase in the Ca2+ concentration in the fluid bathing the thick and thin filaments. Binding of this Ca2+ to the TN-C component triggers a series of conformational transitions in the troponin complex and a change in the position of tropomyosin from a blocking position in the grooves of F-actin. Myosin heads are then able to interact with F-actin and sliding of thick over thin filaments ensues. The research in our laboratory has been directed toward a fuller understanding of the detailed molecular mechanisms by which this intricate and sophisticated system operates in both skeletal and cardiac muscle. To this end we have explored the calcium-induced conformational change in TN-C and its propagation through the entire troponin-tropomyosin complex, using a combination of hydrodynamic (ultracentrifuge, viscosity, magnetic densitometry) and spectroscopic (CD, UV absorption difference, solvent perturbation difference, nmr, and fluorescence) approaches. Our studies to date have included the following: the development of highly purified troponin subunits, using high-performance liquid chromatography methodologies; the rigorous physicochemical characterization of the troponin subunits and their interaction properties; precise details of several of the functional groups (carboxyls, aromatics) involved in the Ca2+-induced conformational change in TN-C; the role of sulfhydryl groups in generating functionally active and conformationally sensitive troponin complexes; the molecular morphology of the troponin complex on the thin filament; the role of the two Ca2+-specific regulatory sites in TN-C in terms of their responsiveness to rapid Ca2+ transients; and the demonstration of a common regulatory mechanism for both skeletal and cardiac muscle, using bioassay and spectroscopic studies on ternary complexes made from hybrid subunits of both muscle types. The highlights of these studies are described, including the recently elucidated x-ray structure of TN-C and how the binding of calcium to such a structure may act as a conformational switch.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 17-residue disulfide-bridged peptide (PAK 128-144) corresponding to the C-terminus of Pseudomonas aeruginosa pilin strain K has been studied by one- and two-dimensional nmr techniques. This synthetic immunogen has been found to exist as two distinct conformations in solution, which have been demonstrated to arise as a result of the isomerization of the I138-P139 amide bond. The two isomers occur in the ratio of 3 : 1 trans to cis at 5°C. Sequential assignments for both forms have been accomplished through the use of nuclear Overhauser enhancement spectroscopy (NOESY) spectra and most side-chain resonances have been assigned using a combination of correlated spectroscopy, total correlated spectroscopy, and NOESY spectra. The presence of the cis isomer, which is considerably more predominant in the oxidized peptide, was confirmed by the observation of the characteristic NOEs between P139 and the preceding residue. Further corroboration was given by the disappearance of the cis resonances in the spectrum of the P139A analogue of PAK 128-144. From observation of the differences in the chemical shifts and amide proton temperature coefficients of the two isomers, it is apparent that the two forms differ markedly in their solution conformation. The biological implications of the isomerization are discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The HPLC retention behavior of three complete single methionine and methionine sulfoxide replacement sets of two 18-mer model peptides and neuropeptide Y (NPY) were investigated. All peptides were prepared by multiple solid-phase peptide synthesis. Plotting the retention time differences between methionine and methionine sulfoxide analogues vs the position of replacement shows that potentially α-helical peptides become helical on binding during reversed-phase high performance liquid chromatography. In the case of an amphipathic α-helix, the retention time differences change periodically with a 3-4 repeat pattern, which allow the location of amphipathic helical structures. Replacements in nonamphipathic α-helical domains cause local preferential binding areas and lead to sequence-dependent retention time profiles. Methionine replacement studies of NPY suggest an unstructured or extended conformation from Tyr1 to Ala12 connected to a well-defined amphipathic α-helix from Pro13 to Arg35. The assignment is confirmed by comparison of nuclear Overhauser effects based two-dimensional 1H-nmr spectroscopy and utilization of the CαH shift index method in 50% trifluoroethanol/50% water. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...