Common Features at the Start of the Neurodegeneration Cascade

A single-molecule study reveals that neurotoxic proteins share common structural features that may trigger neurodegeneration, thus identifying new targets for therapy and diagnosis

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Beckman Laboratories for Structural Biology, Departments of Cell Biology and Biochemistry,

large numbers of protein structures has created a need for automatic and objective methods for the comparison of structures or conformations. Many protein structures show similarities of conformation that are undetectable by comparing their sequences. Comparison of structures can reveal similarities between proteins thought to be unrelated, providing new insight into the interrelationships of sequence, structure and function. Results: Using a new tool that we have developed to perform rapid structural alignment, we present the highlights of an exhaustive comparison of all pairs of Background Although the number of protein structures deposited in the Brookhaven protein database (PDB) has grown rapidly in recent years [I], the subset of new protei

Kinetic analysis provides insight into the mechanism of Ribonuclease A oligomer formation

Ribonuclease A forms a series of oligomers by 3D domain swapping, a possible mechanism for amyloid formation. Using experimental data, the Ribonuclease oligomerization process is analyzed to obtain estimates of individual equilibrium and microscopic rate constants. The results suggest several novel insights into Ribonuclease oligomer formation: (i) two dimers may combine to yield tetramers, (ii) the lower abundance of the cyclic trimer could be ascribed to the cis conformation of its Asn113-Pro114 peptide bonds, (iii) oligomers become the dominant species at very high protein concentrations or upon applying a modest tenfold increase in the equilibrium constants (iv) the rate constants for trimer and tetramer formation are faster than those of dimer formation and (v) glycosylation affects the relative populations of different trimer and tetramer species. By mass spectrometry, oligomers as large as tetradecamers are detected. These results are consistent with the proposal that 3D domain swapping is a mechanism for amyloid formation

SARS-CoV-2 Nsp8 N-terminal domain folds autonomously and binds dsRNA

8 pags., 3 figs.The SARS-CoV-2 Nsp8 protein is a critical component of the RNA replicase, as its N-terminal domain (NTD) anchors Nsp12, the RNA, and Nsp13. Whereas its C-terminal domain (CTD) structure is well resolved, there is an open debate regarding the conformation adopted by the NTD as it is predicted as disordered but found in a variety of complex-dependent conformations or missing from many other structures. Using NMR spectroscopy, we show that the SARS CoV-2 Nsp8 NTD features both well folded secondary structure and disordered segments. Our results suggest that while part of this domain corresponding to two long α-helices forms autonomously, the folding of other segments would require interaction with other replicase components. When isolated, the α-helix population progressively declines towards the C-termini but surprisingly binds dsRNA while preserving structural disorder.Carlos III Institute of Health and the Spanish Ministry of Science and Innovation [COV20/00764 to M.M. and D.V.L.]; MCIN/AEI/10.13039/501100011033 [PID2020-113907RA-I00 to M.M.]; cofunded by the European Union (ERC) [101042403-BiFOLDOME]; Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council; Neither the European Union nor the granting authority can be held responsible for them; NMR experiments were performed in the ‘Manuel Rico’ NMR Laboratory (LMR) of the Spanish National Research Council (CSIC), a node of the Spanish Large-Scale National Facility for Biomolecular NMR (ICTS R-LRB). Funding for open access charge: Ministerio de Ciencia e InnovacionInstituto ´ de Salud Carlos III [COV20/00764].Peer reviewe

Dimerization and folding processes of Treponema denticola cystalysin: the role of pyridoxal 5'-phosphate.

Cystalysin, the key virulence factor in the bacterium Treponema denticola responsible for periodontitis, is a homodimeric pyridoxal 5'-phosphate (PLP)-C-S lyase. The dimerization process and the urea-induced unfolding equilibrium of holocystalysin were compared with those of the apo form. The presence of PLP decreases approximately 4 times the monomer-dimer equilibrium dissociation constant. By using a variety of spectroscopic and analytical procedures, we demonstrated a difference in their unfolding profiles. Upon the monomerization of apocystalysin, occurring between 1 and 2 M urea, a self-associated equilibrium intermediate with a very high beta-sheet content is stabilized over the 2.5-4 M urea range, giving rise to a fully unfolded monomer at higher urea concentrations. On the other hand, highly destabilizing conditions, accompanied by the formation of a significant amount of insoluble aggregates, are required for PLP release and monomerization. Refolding studies, together with analysis of the dissociation/association process of cystalysin, shed light on how the protein concentration and the presence or absence of PLP under refolding conditions could affect the recovery of the active dimeric enzyme and the production of insoluble aggregates. When the protein is completely denatured, the best reactivation yield found was approximately 50% and 25% for holo and apocystalysin, respectively. The dimerization and folding processes of cystalysin have been compared with those of another PLP C-S lyase, MalY from E. coli, and the possible relevance of their PLP binding mode in these processes has been discussed

"Structural preferences of the protein hCPEB3 in the prelude to memory consolidation"

Structural Preferences of the Protein hCPEB3 in the Prelude to Memory Consolidation 1213 Douglas Laurents , Daniel Ramírez De Mingo , David Pantoja Uceda , Rubén Hervás , Mariano Carrión Vázquez 1) "Rocasolano" Institute for Physical Chemistry, Madrid, Spain 2) Instituto Cajal, IC-CSIC, Madrid, Spain 3) School of Biomedical Sciences, The University of Hong Kong, Pokfulam, Hong Kong, China How are memories stored in the brain? Neurospecific forms of the cytoplasmic polyadenylation element binding protein (CPEB) are thought to promote memory consolidation by undergoing a disordered to functional amyloid conformational transformation at specific dendritic spines(1). This alters local mRNA translation and leads to a strengthening of particular dendritic spines(2). Whereas the structure of the Drosophila CPEB homolog has been recently elucidated(3), how amyloid formation occurs in the human homolog (hCPEB3) is still unclear. To address this question, we have characterized the partial structure and dynamics of the 426- residue disordered region in hCPEB3 by NMR spectroscopy(4). Five segments with partial ¿- helix formation, two with moderate polyproline II helix populations and a rigid hydrophobic segment were observed in the first 250 residues. Biophysical assays evince that residues 251- 426 can promote biomolecular condensateformation (5). Some evidence for interactions among the elements of partly populated ¿-helices and between the polyproline II helices with profilin were observed. Profilin binds both polyproline II helices and actin and could mediate dendritic spine specific fortification of the actincytoskeleton. These results provide a hypothetical working model for understanding hCPEB3 amyloid formation and its role in memory consolidation. 1. Si K, Linquist S, Kandel ER (2003) Cell 115: 897-891 2. Si K & Kandel ER (2016) Cold Spring Harb Perspect Biol. 8:a021774 3. Hervás R. ..et al.. Si K. (2020) Science 367: 1230-1234 4. Ramírez de Mingo D. ..et al.. Laurents DV. (2021) BMC Biol. 20: 129. 5. Ramírez de Mingo D. ..et al.. Carrión-Vázquez M, bioRxiv 2020.2020.06.0212978