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The aggregation of amyloidogenic proteins is often related to the occurrence of neurodegenerative diseases, including fused in sarcoma protein (FUS) in frontotemporal lobar degeneration and amyotrophic lateral sclerosis diseases. Recently, the SERF protein family has been reported to have a significant regulatory effect on amyloid formation, but it is still unclear about the detailed mechanisms of SERF acting on different amyloidogenic proteins. Herein, nuclear magnetic resonance (NMR) spectroscopy and fluorescence spectroscopy were used to explore interactions of ScSERF with three amyloidogenic proteins FUS‐LC, FUS‐Core, and α‐Synuclein. NMR chemical shift perturbations reveal them sharing similar interaction sites on the N‐terminal region of ScSERF. However, the amyloid formation of α‐Synuclein protein is accelerated by ScSERF, while ScSERF inhibits fibrosis of FUS‐Core and FUS‐LC proteins. Both the primary nucleation and the total amount of fibrils produced are detained. Our results suggest a diverse role of ScSERF in regulating the fibril growth of amyloidogenic proteins. [ABSTRACT FROM AUTHOR]

The glutamine binding protein (GlnBP) binds l-glutamine and cooperates with its cognate transporters during glutamine uptake. Crystal structure analysis has revealed an open and a closed conformation for apo- and holo-GlnBP, respectively. However, the detailed conformational dynamics have remained unclear. Herein, we combined NMR spectroscopy, MD simulations, and single-molecule FRET techniques to decipher the conformational dynamics of apo-GlnBP. The NMR residual dipolar couplings of apo-GlnBP were in good agreement with a MD-derived structure ensemble consisting of four metastable states. The open and closed conformations are the two major states. This four-state model was further validated by smFRET experiments and suggests the conformational selection mechanism in ligand recognition of GlnBP. [ABSTRACT FROM AUTHOR]

We used Xenopus laevis oocytes, a paradigm for a variety of biological studies, as a eukaryotic model system for in-cell protein NMR spectroscopy. The small globular protein GB1 was one of the first studied in Xenopus oocytes, but there have been few reports since then of high-resolution spectra in oocytes. The scarcity of data is at least partly due to the lack of good labeling strategies and the paucity of information on resonance broadening mechanisms. Here, we systematically evaluate isotope enrichment and labeling methods in oocytes injected with five different proteins with molecular masses of 6 to 54 kDa. 19F labeling is more promising than 15N, 13C, and 2H enrichment. We also used 19F NMR spectroscopy to quantify the contribution of viscosity, weak interactions, and sample inhomogeneity to resonance broadening in cells. We found that the viscosity in oocytes is only about 1.2 times that of water, and that inhomogeneous broadening is a major factor in determining line width in these cells. [ABSTRACT FROM AUTHOR]

Protein mobility in living cells is vital for cell function. Both cytosolic viscosity and weak protein-protein interactions affect mobility, but examining viscosity and weak interaction effects is challenging. Herein, we demonstrate the use of 19F NMR spectroscopy to measure cytoplasmic viscosity and to characterize nonspecific protein-protein interactions in living Escherichia coli cells. The origins of resonance broadening in Escherichia coli cells were also investigated. We found that sample inhomogeneity has a negligible effect on resonance broadening, the cytoplasmic viscosity is only about 2-3 times that of water, and ubiquitous transient weak protein-protein interactions in the cytosol play a significant role in governing the detection of proteins by using in-cell NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The Ca2+-mediated conformational transition of the protein calmodulin (CaM) is essential to a variety of signal transduction pathways. Whether the transition in living cells is similar to that observed in buffer is not known. Here, we report the direct observation by 19F NMR spectroscopy of the transition of the Ca2+-free and -bound forms in Xenopus laevis oocytes at different Ca2+ levels. We find that the Ca2+-bound CaM population increased greatly upon binding the target protein myosin light-chain kinase (MLCK) at the same Ca2+ level. Paramagnetic NMR spectroscopy was also exploited for the first time to obtain long-range structural constraints in cells. Our study shows that 19F NMR spectroscopy can be used to obtain long-range structural constraints in living eukaryotic cells and paves the way for quantification of protein binding constants. [ABSTRACT FROM AUTHOR]

NMR Spectroscopy In their Communication on page 8686 ff., C. Li et al., demonstrate that 19F labeling is a good first choice for studying globular and disordered proteins in Xenopus oocytes, especially compared with conventional 15N ‐ or 13C ‐ methyl enrichment. By using 19F labeling, they found that, unlike E. coli cells, the viscosity in oocytes is only about 1.2 times that of water and that inhomogeneous broadening contributes 60 – 70 % to the line width. The labeling strategies and resonance broadening mechanisms in Xenopus oocytes were explored with the goal of expanding the application of this cell type. [ABSTRACT FROM AUTHOR]

A protein gel electrophoresis procedure using 0.05% w/v sarkosyl, is reported. The method called 05SAR-PAGE can be used to identify the native masses, dimeric states and modification states of proteins, and also be suitable for pursuing native electroblotting and immunodetection. It has been demonstrated by NMR spectroscopy that 0.05% w/v SAR is much milder than SDS, so it has subtle effects on the native structure of proteins. Therefore, the non-covalent dimerization of PhoB N and PhoR cp can be identified by 05SAR-PAGE which cannot be observed by SDS-PAGE. It has also been demonstrated that 05SAR-PAGE can be used to identify the phosphorylated or methylated proteins. Besides, 05SAR-PAGE shows the advantages of simple operation and low cost, and can be easily adapted to diverse applications. Image 1 • Determination of the dimerization states of PhoB N and PhoR cp by 05SAR-PAGE. • Mild effect of SAR on protein structure. • Western-blot of monomer and dimer states in vivo by 05SAR-PAGE. • Identification of different modification states of proteins by 05SAR-PAGE. [ABSTRACT FROM AUTHOR]

Abstract: α-Synuclein is involved in Parkinson's disease and its interaction with cell membrane is crucial to its pathological and physiological functions. Membrane properties, such as curvature and lipid composition, have been shown to affect the interactions by various techniques, but ion effects on α-synuclein membrane interactions remain elusive. Ca2+ dynamic fluctuation in neurons plays important roles in the onset of Parkinson's disease and its influx is considered as one of the reasons to cause cell death. Using solution Nuclear Magnetic Resonance (NMR) spectroscopy, here we show that Ca2+ can modulate α-synuclein membrane interactions through competitive binding to anionic lipids, resulting in dissociation of α-synuclein from membranes. These results suggest a negative modulatory effect of Ca2+ on membrane mediated normal function of α-synuclein, which may provide a clue, to their dysfunction in neurodegenerative disease. [Copyright &y& Elsevier]