Weak long-range correlated motions in a surface patch of ubiquitin involved in molecular recognition.

[Image: see text] Long-range correlated motions in proteins are candidate mechanisms for processes that require information transfer across protein structures, such as allostery and signal transduction. However, the observation of backbone correlations between distant residues has remained elusive, and only local correlations have been revealed using residual dipolar couplings measured by NMR spectroscopy. In this work, we experimentally identified and characterized collective motions spanning four β-strands separated by up to 15 Å in ubiquitin. The observed correlations link molecular recognition sites and result from concerted conformational changes that are in part mediated by the hydrogen-bonding network

Hsp70 oligomerization is mediated by an interaction between the interdomain linker and the substrate-binding domain

Oligomerization in the heat shock protein (Hsp) 70 family has been extensively documented both in vitro and in vivo, although the mechanism, the identity of the specific protein regions involved and the physiological relevance of this process are still unclear. We have studied the oligomeric properties of a series of human Hsp70 variants by means of nanoelectrospray ionization mass spectrometry, optical spectroscopy and quantitative size exclusion chromatography. Our results show that Hsp70 oligomerization takes place through a specific interaction between the interdomain linker of one molecule and the substrate-binding domain of a different molecule, generating dimers and higher-order oligomers. We have found that substrate binding shifts the oligomerization equilibrium towards the accumulation of functional monomeric protein, probably by sequestering the helical lid sub-domain needed to stabilize the chaperone: substrate complex. Taken together, these findings suggest a possible role of chaperone oligomerization as a mechanism for regulating the availability of the active monomeric form of the chaperone and for the control of substrate binding and release

Disulfide bonds reduce the toxicity of the amyloid fibrils formed by an extracellular protein

In a stable condition: Disulfide bonds stabilize folded proteins primarily by decreasing the entropic cost of folding. Such cross-links also reduce toxic aggregation by favoring the formation of highly structured amyloid fibrils (see picture). It is suggested that disulfide bonds in extracellular proteins were selected by evolutionary pressures because they decrease the propensity to form toxic aggregates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Inhibition of a-Synuclein Aggregation and Mature Fibril Disassembling With a Minimalistic Compound, ZPDm

Synucleinopathies are a group of disorders characterized by the accumulation of a-Synuclein amyloid inclusions in the brain. Preventing a-Synuclein aggregation is challenging because of the disordered nature of the protein and the stochastic nature of fibrillogenesis, but, at the same time, it is a promising approach for therapeutic intervention in these pathologies. A high-throughput screening initiative allowed us to discover ZPDm, the smallest active molecule in a library of more than 14.000 compounds. Although the ZPDm structure is highly related to that of the previously described ZPD-2 aggregation inhibitor, we show here that their mechanisms of action are entirely different. ZPDm inhibits the aggregation of wild-type, A30P, and H50Q a-Synuclein variants in vitro and interferes with a-Synuclein seeded aggregation in protein misfolding cyclic amplification assays. However, ZPDm distinctive feature is its strong potency to dismantle preformed a-Synuclein amyloid fibrils. Studies in a Caenorhabditis elegans model of Parkinson’s Disease, prove that these in vitro properties are translated into a significant reduction in the accumulation of a-Synuclein inclusions in ZPDm treated animals. Together with previous data, the present work illustrates how different chemical groups on top of a common molecular scaffold can result in divergent but complementary anti-amyloid activities

Androgen receptor condensates as drug targets

Transcription factors are among the most attractive therapeutic targets, but are considered largely undruggable. Here we provide evidence that small molecule-mediated partitioning of the androgen receptor, an oncogenic transcription factor, into phase-separated condensates has therapeutic effect in prostate cancer models. We show that the phase separation capacity of the androgen receptor is driven by aromatic residues and short unstable helices in its intrinsically disordered activation domain. Based on this knowledge, we developed tool compounds that covalently attach aromatic moieties to cysteines in the receptors’ activation domain. The compounds enhanced partitioning of the receptor into condensates, facilitated degradation of the receptor, inhibited androgen receptor-dependent transcriptional programs, and had antitumorigenic effect in models of prostate cancer and castration-resistant prostate cancer in vitro and in vivo. These results establish a generalizable framework to target the phase- separation capacity of intrinsically disordered regions in oncogenic transcription factors and other disease-associated proteins with therapeutic intent

Determination of Conformational Equilibria in Proteins Using Residual Dipolar Couplings

In order to carry out their functions, proteins often undergo significant conformational fluctuations that enable them to interact with their partners. The accurate characterization of these motions is key in order to understand the mechanisms by which macromolecular recognition events take place. Nuclear magnetic resonance spectroscopy offers a variety of powerful methods to achieve this result. We discuss a method of using residual dipolar couplings as replica-averaged restraints in molecular dynamics simulations to determine large amplitude motions of proteins, including those involved in the conformational equilibria that are established through interconversions between different states. By applying this method to ribonuclease A, we show that it enables one to characterize the ample fluctuations in interdomain orientations expected to play an important functional role

Toward an accurate determination of free energy landscapes in solution states of proteins

The dynamics of proteins plays a central role in their activity, including enzymatic catalysis and allosteric communication. Many advances have been made in recent years in the characterization of the equilibrium fluctuations of proteins through experimental and computational methods. We present evidence that the use of molecular dynamics simulations with ensemble-averaged structural restraints derived from nuclear magnetic resonance spectroscopy enables the determination of ensembles of structures representing the equilibrium populations of conformations explored during the thermal fluctuations of proteins. We obtained these results by using residual dipolar couplings to characterize the dynamics of ubiquitin and to derive its free-energy landscape under native conditions. © 2009 American Chemical Society