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  • BIOLOGY  (4)
  • 1
    Keywords: RECEPTOR ; SPECTRA ; GENE ; PROTEINS ; BINDING ; BIOLOGY ; ELEMENTS ; STABILITY ; CD4-BINDING DOMAIN ; CONFORMATIONAL SWITCH ; GP120 ; FAMILIES ; POTENTIALS ; SET ; protein conformation ; CD-spectroscopy ; CHAIN INTERACTION INDEX ; conformational rigidity ; helix-inducing tetrads ; peptide folding ; switch peptides
    Abstract: In some naturally occurring protein sequences, an abrupt, concerted refolding from beta-sheet to helical conformation occurs when the polarity of the surrounding medium drops below a critical level. This switch-like behaviour was first observed on the HIV-1 envelope glycoprotein gp120, where it plays a crucial role in the efficient binding of gp120 to the T-cell receptor CD4. Previous work had shown that an N-terminal amino acid tetrad LPCR and a Trp located 5-20 residues downstream to the tetrad are common motifs in polarity-driven switch peptides. The LPCR tetrad governs the folding of the subsequent residues and acts as a helix initiation site, whereas the Trp is responsible for the cooperative character of the structural change due to multiple, simultaneous interactions of its quadrupole moment with several amino acid residues within the sequences. Here we identify and characterize new families of switch peptides that use different, turn-probable tetrads (LPST and VPSR) as helix initiation sites at the N-terminus. We have also been able to demonstrate that some tetrads with extremely high turn probability do not serve as helix initiation sites. Comparison of these with LPCR and the newly discovered tetrads LPST and VPSR has allowed a more comprehensive description of the physico-chemical properties of helix-inducing tetrads. The deeper understanding of the intrinsic properties of switch sequences allows the design of artificial polarity-driven switches, applicable in engineering of, e. g. controllable binding sites in artificial proteins.
    Type of Publication: Journal article published
    PubMed ID: 20878680
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  • 2
    Keywords: PEPTIDE ; SPECTRA ; Germany ; PROTEIN ; BIOLOGY ; MOLECULAR-BIOLOGY ; FUSION ; PEPTIDES ; SECONDARY STRUCTURE ; molecular biology ; molecular ; CHEMISTRY ; methods ; USA ; SPECTRUM
    Type of Publication: Journal article published
    PubMed ID: 17320030
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  • 3
    Keywords: ENVIRONMENT ; APOPTOSIS ; EXPRESSION ; GROWTH ; tumor ; CELL ; Germany ; human ; KINASE ; SITE ; TISSUE ; BINDING ; BIOLOGY ; fibroblasts ; MOLECULAR-BIOLOGY ; PHOSPHORYLATION ; ACID ; DESIGN ; MODULATION ; DERIVATIVES ; LIGANDS ; NETHERLANDS ; LECTIN ; STRUCTURAL-CHANGES ; HUMAN NEUROBLASTOMA-CELLS ; molecular biology ; molecular ; RE ; INCREASE ; NUCLEAR ; enzymatic ; modification ; FUNCTIONALITY ; amino acids ; MAMMALIAN LECTINS ; CARBOHYDRATE-BINDING PROTEIN-35 ; GANGLIOSIDE GM(1) ; histochemistry ; serine phosphorylation ; titania chromatography
    Abstract: Galectin-3 has a unique modular design. Its short N-terminal stretch can be phosphorylated, relevant for nuclear export and anti-anoikis/apoptosis activity. Enzymatic modification by casein kinase 1 at constant ATP concentration yielded mg quantities of mono- and diphosphorylated derivatives at Ser5/Ser11 in a 2:1 ratio. Their carbohydrate-inhibitable binding to asialofetuin, cell surfaces of three tumor lines, rabbit erythrocytes leading to haemagglutination and cytoplasmic sites in fixed tissue sections was not markedly altered relative to phosphate-free galectin-3. Spectroscopically, phosphorylation induced alterations in the far UV CD, indicative of an increase in ordered structure. This is accompanied by changes in the environment of aromatic amino acids signified by shifts in the near UV CD. (C) 2008 Elsevier B.V. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 18302943
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  • 4
    Keywords: PEPTIDE ; Germany ; PROTEIN ; PROTEINS ; MECHANISM ; BIOLOGY ; MOLECULAR-BIOLOGY ; MEMBRANE ; FUSION ; FUSION PROTEINS ; CRYSTAL-STRUCTURE ; PEPTIDES ; SECONDARY STRUCTURE ; DOMAINS ; FUSION PROTEIN ; molecular biology ; molecular ; RE ; GLYCINE ; INFLUENZA HEMAGGLUTININ ; MUTATIONAL ANALYSIS ; VIRAL MEMBRANE-FUSION ; analysis ; ENVELOPE PROTEIN ; TRANSMEMBRANE DOMAIN ; viral ; circular dichroism ; AVIAN-SARCOMA ; LEUKOSIS VIRUS ; membrane fusion ; VIRUS GLYCOPROTEIN-G
    Abstract: Membrane fusion is essential for many biological processes. Though there hove been many structure and fusion studies of cel lular and viral fusion proteins in the last years, their functional mechanism remains elusive. In particular, the structural modes of operation of the transmembrane domains and viral fusion peptides of fusion proteins during membrane fusion have not been elucidated, although work on de novo designed fusogenic peptides suggested that conformational flexibility was necessary. In addition, the use of different and incompatible measurement criteria has made a comparative overview difficult. Here, we report a systematic structural analysis of viral fusion peptides from different fusion protein classes and transmembrane domains of viral and cellular fusion proteins by using circular dichroism spectroscopy. The data that were obtained demonstrate that class viral fusion peptides show a structural flexibility between helix and irregular secondary structures, whereas fusion peptides of class II viral fusion proteins are characterized by a stable random coil and turn structure. Thus, conformational flexibility does not seem to be a universal criterion for the fusion activity of a fusion peptide. On the contrary, the transmembrane domains of fusion proteins are distinguished by a structural flexibility between helix and sheet structure that is similar to de novo designed unnatural peptides with high fusion activities (M. W. Hofmann et al. PNAS 2004, 101, 14776-14781). Thus, the conformational behavior of the fusogenic unnatural peptides most closely resembles that of, fusion protein transmembrane domains, and allows them to be used to gain a deeper understanding of the membrane fusion process
    Type of Publication: Journal article published
    PubMed ID: 18330852
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