@article{ArgosDandekar1994,
  author    = {Argos, P. and Dandekar, Thomas},
  title     = {Delineating the main chain topology of four-helix bundle proteins using the genetic algorithm and knowledge based on the amino acid sequence alone},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-33807},
  year      = {1994},
  abstract  = {No abstract available},
  subject      = {Proteine},
  language  = {en}
}
@phdthesis{PatinoGonzalez2007,
  author    = {Pati{\~n}o Gonzalez, Edwin},
  title     = {Functional Studies and X-Ray Structure Analysis of Human Interleukin-5 Receptor Alpha and Human Interleukin-5 Complex},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-27319},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2007},
  abstract  = {Interleukin-5 (IL-5) is a member of the hematopoietic class I cytokines and is specifically involved in eosinophil activation. IL-5 plays an important role in disease conditions such as allergic asthma and other hypereosinophilias, which are characterized by highly increased levels of eosinophils in peripheral blood and tissues. The IL-5 receptor is a heterodimer consisting of a binding alpha subunit (IL- 5R\&\#945;) and a common beta subunit (IL-5R\&\#946;). This IL-5R\&\#946; is shared with the IL-3 and GM-CSF receptors. The IL-5R\&\#945; is required for ligand-specific binding, whereas the association of the IL-5R\&\#946; subunit triggers intracellular signal transduction. Previous studies have described the crystallographic structure of human IL-5 (hIL-5), as well as that of the common IL-5R\&\#946; chain (IL-5R\&\#946;c) However, no experimental structural data are yet available for the interaction of the high-affinity IL-5 receptor IL-5R\&\#945; with its ligand IL-5. Therefore, this thesis had the principle objective to gain new insights into the basis of this important agonist-receptor interaction. In particular, data on the recombinant expression, purification and preparation of the binary complex of hIL-5 bound to the receptor ectodomain of hIL-5R\&\#945; are shown, as well as the subsequent crystal structure analysis of the binary ligand-receptor (hIL-5R\&\#945;/hIL-5) complex. Both proteins were expressed in an Escherichia coli expression system, purified to homogeneity, and crystallized. However, since the initial analysis of these crystals did not show any X-ray diffraction, each step of the preparation and crystallization procedure had to be stepwise optimized. Several improvements proved to be crucial for obtaining crystals suitable for structure analysis. A free cysteine residue in the N-terminal domain of the hIL-5R\&\#945; ectodomain protein was mutated to alanine to remove protein heterogeneity. In addition, hIL-5 affinity chromatography of the receptor protein proved to be absolutely crucial for crystal quality. Additive screening using the initial crystallization condition finally yielded crystals of the binary complex, which diffracted to 2.5{\AA} resolution and were suitable for structure analysis. The preliminary structure data demonstrate a new receptor architecture for the IL-5R\&\#945; ligand-binding domain, which has no similarities to other cytokine class I receptor structures known so far. The complex structure demonstrates that the ligand-binding region of human IL-5R\&\#945; is dispersed over all three extracellular domains, and adopts a binding topology in which the cytokine recognition motif (CRM) needs the first Fn-III domain of the human IL-5R\&\#945; to bind the ligand. In a second project, a prokaryotic expression system for murine IL-5 (mIL-5) was established to allow the production of mIL-5 and mIL-5 antagonist that should facilitate functional studies in mice. Since the expression of mIL-5 in E. coli had never been successful so far, a fusion protein system was generated expressing high yields of mIL-5. Chemical cleavage with cyanogen bromide (CNBr) was used to release mIL-5 monomers, which were subsequently purified and refolded. This technique yielded an active murine IL-5 dimer as confirmed by TF-1 cell proliferation assays. The protein was crystallized and the structure of mIL-5 could be determined at 2.5{\AA} resolution. The molecular structure revealed a symmetrical left-handed four helices bundle dimer similar to human IL-5. Analysis of the structure-/function relationship allowed us to design specific mIL-5 antagonist molecules, which are still under examination. Taken together, these findings provide further insights in the IL-5 and IL-5R interaction which may help to further understand and depict this and other cytokine-receptor interactions of similar architecture, e.g. the IL-13 ligand-receptor system. Ultimately, this may represent another piece of puzzle in the attempts to rationally design and engineer novel IL-5-related pharmacological therapeutics.},
  subject      = {Functional Studies},
  language  = {en}
}
@phdthesis{Delto2015,
  author    = {Delto, Carolyn Francesca},
  title     = {Structural and Biochemical Characterization of the GABA(A) Receptor Interacting Protein Muskelin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115922},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {In a study from 2011, the protein muskelin was described as a central coordinator of the retrograde transport of GABA(A) receptors in neurons. As muskelin governs the transport along actin filaments as well as microtubules, it might be the first representative of a novel class of regulators, which coordinate cargo transport across the borders of these two independent systems of transport paths and their associated motorproteins. To establish a basis for understanding the mode of operation of muskelin, the aim of this thesis was an in-depth biochemical and structural characterization of muskelin and its interaction with the GABA(A) receptor. One focus of the work was the analysis of the oligomerization of muskelin. As could be demonstrated, the oligomerization is based on two independent interactions mediated by different domains of the protein: a known interaction of the N-terminal discoidin domain with the C-terminal portion, termed head-to-tail interaction, and a dimerization of the LisH motif in muskelin that was so far neglected in the literature. For the detailed studies of both binding events, the solution of a crystal structure of a fragment of muskelin, comprising the Discoidin domain and the LisH motif, was an important basis. The fragment crystallized as a dimer, with dimerization being mediated solely by the LisH motif. Biochemical analysis corroborated that the LisH motif in muskelin serves as a dimerization element, and, moreover, showed that the C-terminal domain of the protein substantially stabilizes this dimerization. In addition, the crystal structure revealed the molecular composition of the surface of the head in the head-to-tail interaction, namely the discoidin domain. This information enabled to map the amino acids contributing to binding, which showed that the binding site of the head-to-tail interaction coincides with the generic ligand binding site of the discoidin domain. As part of the analyses, residues that are critical for LisH-dimerization and the head-to-tail binding, respectively, were identified, whose mutation specifically interfered with each of the interactions separately. These mutations allowed to investigate the interplay of these interactions during oligomerization. It could be shown that recombinant muskelin assembles into a tetramer to which both interactions, the LisH-dimerization and the head-to-tail binding, contribute independently. When one of the two interactions was disturbed, only a dimer mediated via the respective other interaction could be formed; when both interactions were disturbed, the protein was present as monomer. Furthermore, Frank Heisler in the group of Matthias Kneussel was able to show the drastic impact of an impaired LisH-dimerization on muskelin in cells using these mutations. Disturbing the LisH-dimerization led to a complete redistribution of the originally cytoplasmic muskelin to the nucleus which was accompanied by a severe impairment of its function during GABA(A) receptor transport. Following up on these results in an analysis of muskelin variants, for which alterations of the subcellular localization had been published earlier, the crucial influence of LisH-dimerization to the subcellular localization and thereby the role of muskelin in the cell was confirmed. The biochemical studies of the interaction of muskelin and the alpha1 subunit of the GABA(A) receptor demonstrated a direct binding with an affinity in the low micromolar range, which is mediated primarily by the kelch repeat domain in muskelin. For the binding site on the GABA(A) receptor, it was confirmed that the thirteen most C-terminal residues of the intracellular domain are critical for the binding of muskelin. In accordance with the strong conservation of these residues among the alpha subunits of the GABA(A) receptor, it could be shown that an interaction with muskelin in vitro is also possible for the alpha2 and alpha5 subunits. Based on the comparison of the binding sites between the homologous subunits, tentative conclusions can be drawn about the details of the binding, which may serve as a starting point for follow-up studies. This thesis thereby makes valuable contributions to the understanding of muskelin, in particular the significance of its oligomerization. It furthermore provides an experimental framework for future studies that address related topics, such as the characterization of other muskelin interaction partners, or the questions raised in this work.},
  subject      = {Oligomerisation},
  language  = {en}
}