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Disordered Regions (disordered + regions)
Selected AbstractsDynamic interactions of proteins in complex networks: a more structured viewFEBS JOURNAL, Issue 19 2009Amelie Stein Virtually every process in a cell is carried out by macromolecular complexes whose actions need to be perfectly orchestrated. The synchronization and regulation of these biological functions is indeed critical and is usually carried out by complex networks of transient protein interactions. Here, we review some of the many strategies that proteins in regulatory networks use to achieve the dynamic plasticity necessary to rapidly respond to diverse cellular needs. More specifically, we present recent work on the molecular bases of transient peptide-mediated interactions and the role that post-translational modifications and disordered regions might play. Finally, in light of some recent findings, we speculate on the possibility of a new regulatory code for intrinsically disordered proteins and the potential biophysical and functional advantages that disorder might provide. [source] Isotropic "Islands" in a Cholesteric "Sea": Patterned Thermal Expansion for Responsive Surface Topologies,ADVANCED MATERIALS, Issue 14 2006E. Sousa A method to capture ordered and disordered regions in reactive mesogen films to take advantage of the anisotropic thermal properties and fabricate a thermally responsive patterned film is presented. The image shows white-light interferometer images of isotropic cylinders in cholesteric material. The underlying principle phenomenon observed here is well described by a finite-element simulation. [source] Functional dissection of an intrinsically disordered protein: Understanding the roles of different domains of Knr4 protein in protein,protein interactionsPROTEIN SCIENCE, Issue 7 2010Adilia Dagkessamanskaia Abstract Knr4, recently characterized as an intrinsically disordered Saccharomyces cerevisiae protein, participates in cell wall formation and cell cycle regulation. It is constituted of a functional central globular core flanked by a poorly structured N-terminal and large natively unfolded C-terminal domains. Up to now, about 30 different proteins have been reported to physically interact with Knr4. Here, we used an in vivo two-hybrid system approach and an in vitro surface plasmon resonance (BIAcore) technique to compare the interaction level of different Knr4 deletion variants with given protein partners. We demonstrate the indispensability of the N-terminal domain of Knr4 for the interactions. On the other hand, presence of the unstructured C-terminal domain has a negative effect on the interaction strength. In protein interactions networks, the most highly connected proteins or "hubs" are significantly enriched in unstructured regions, and among them the transient hub proteins contain the largest and most highly flexible regions. The results presented here of our analysis of Knr4 protein suggest that these large disordered regions are not always involved in promoting the protein,protein interactions of hub proteins, but in some cases, might rather inhibit them. We propose that this type of regions could prevent unspecific protein interactions, or ensure the correct timing of occurrence of transient interactions, which may be of crucial importance for different signaling and regulation processes. [source] Identification of transient hub proteins and the possible structural basis for their multiple interactionsPROTEIN SCIENCE, Issue 1 2008Miho Higurashi Abstract Proteins that can interact with multiple partners play central roles in the network of protein,protein interactions. They are called hub proteins, and recently it was suggested that an abundance of intrinsically disordered regions on their surfaces facilitates their binding to multiple partners. However, in those studies, the hub proteins were identified as proteins with multiple partners, regardless of whether the interactions were transient or permanent. As a result, a certain number of hub proteins are subunits of stable multi-subunit proteins, such as supramolecules. It is well known that stable complexes and transient complexes have different structural features, and thus the statistics based on the current definition of hub proteins will hide the true nature of hub proteins. Therefore, in this paper, we first describe a new approach to identify proteins with multiple partners dynamically, using the Protein Data Bank, and then we performed statistical analyses of the structural features of these proteins. We refer to the proteins as transient hub proteins or sociable proteins, to clarify the difference with hub proteins. As a result, we found that the main difference between sociable and nonsociable proteins is not the abundance of disordered regions, in contrast to the previous studies, but rather the structural flexibility of the entire protein. We also found greater predominance of charged and polar residues in sociable proteins than previously reported. [source] Quantitative assessment of the structural bias in protein,protein interaction assaysPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 22 2008Åsa K. Björklund Abstract With recent publications of several large-scale protein,protein interaction (PPI) studies, the realization of the full yeast interaction network is getting closer. Here, we have analysed several yeast protein interaction datasets to understand their strengths and weaknesses. In particular, we investigate the effect of experimental biases on some of the protein properties suggested to be enriched in highly connected proteins. Finally, we use support vector machines (SVM) to assess the contribution of these properties to protein interactivity. We find that protein abundance is the most important factor for detecting interactions in tandem affinity purifications (TAP), while it is of less importance for Yeast Two Hybrid (Y2H) screens. Consequently, sequence conservation and/or essentiality of hubs may be related to their high abundance. Further, proteins with disordered structure are over-represented in Y2H screens and in one, but not the other, large-scale TAP assay. Hence, disordered regions may be important both in transient interactions and interactions in complexes. Finally, a few domain families seem to be responsible for a large part of all interactions. Most importantly, we show that there are method-specific biases in PPI experiments. Thus, care should be taken before drawing strong conclusions based on a single dataset. [source] Ultralow-resolution ab initio phasing of filamentous proteins: crystals from a six-Ig fragment of titin as a case studyACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2008Alexandre Urzhumtsev Low-resolution diffraction data (resolution below 12,Å) from crystals of a filamentous six-Ig fragment of titin, I65,I70, were used in ab initio phasing with the aim of calculating its lattice packing and molecular envelope. Filamentous molecules, characterized by marked anisometry and idiosyncratic crystal lattices, have not been addressed before using this methodology. In this study, low-resolution phasing (19,122,Å) successfully identified the region of the unit cell occupied by the molecule. Phase extension to a higher resolution (12,Å) yielded regions of high density that corresponded either to the positions of individual Ig domains or to zones of dense intermolecular contacts, hindering the identification of individual domains and the interpretation of electron-density maps in terms of a molecular model. This problem resulted from the acutely uneven packing of the molecules in the crystal and it was further accentuated by the presence of partially disordered regions in the molecule. Addition of low-resolution reflections with phases computed ab initio to those obtained experimentally using MIRAS improved the initial electron-density maps of the atomic model, demonstrating the generic utility of low-resolution phases for the structure-elucidation process, even when individual molecules cannot be resolved in the lattice. [source] A strained DNA binding helix is conserved for site recognition, folding nucleation, and conformational modulation,BIOPOLYMERS, Issue 6 2009Diana E. Wetzler Abstract Nucleic acid recognition is often mediated by ,-helices or disordered regions that fold into ,-helix on binding. A peptide bearing the DNA recognition helix of HPV16 E2 displays type II polyproline (PII) structure as judged by pH, temperature, and solvent effects on the CD spectra. NMR experiments indicate that the canonical ,-helix is stabilized at the N-terminus, while the PII forms at the C-terminus half of the peptide. Re-examination of the dihedral angles of the DNA binding helix in the crystal structure and analysis of the NMR chemical shift indexes confirm that the N-terminus half is a canonical ,-helix, while the C-terminal half adopts a 310 helix structure. These regions precisely match two locally driven folding nucleii, which partake in the native hydrophobic core and modulate a conformational switch in the DNA binding helix. The peptide shows only weak and unspecific residual DNA binding, 104 -fold lower affinity, and 500-fold lower discrimination capacity compared with the domain. Thus, the precise side chain conformation required for modulated and tight physiological binding by HPV E2 is largely determined by the noncanonical strained ,-helix conformation, "presented" by this unique architecture. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 432,443, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | ||||||||||||||||||||||