Sudden cardiac death in synucleinopathies.

The purpose of this study was to investigate the cause of death in subjects with α-synucleinopathies (ASs) and the confirmed presence of cardiac α-synuclein (α-syn), compared to non-AS disorders in a neuropathologically confirmed cohort. In total, 78 neuropathologically confirmed AS cases positive for cardiac α-syn were included in the study. Individuals with other neurocognitive diseases, having no α-syn in the brainstem or above, nor in cardiac nerves, served as controls (n = 53).

Cardiac Alpha-Synuclein Is Present in Alpha-Synucleinopathies.

Background: Alpha-synucleinopathies (AS) are characterized by pathologic aggregations of alpha-synuclein (α-syn) in the central nervous system, and comprise dementia with Lewy bodies, Parkinson's disease, and multiple system atrophy. Previous studies on AS have reported findings of α-syn pathology in the peripheral nervous system of multiple organs, including the heart.

Objective: The aim of this study was to further investigate and confirm the presence of cardiac α-syn in AS compared to other major neurocognitive disorders in a neuropathologically confirmed cohort.

Functional Differentiation of Antiporter-Like Polypeptides in Complex I; a Site-Directed Mutagenesis Study of Residues Conserved in MrpA and NuoL but Not in MrpD, NuoM, and NuoN.

It has long been known that the three largest subunits in the membrane domain (NuoL, NuoM and NuoN) of complex I are homologous to each other, as well as to two subunits (MrpA and MrpD) from a Na+/H+ antiporter, Mrp. MrpA and NuoL are more similar to each other and the same is true for MrpD and NuoN. This suggests a functional differentiation which was proven experimentally in a deletion strain model system, where NuoL could restore the loss of MrpA, but not that of MrpD and vice versa.

A De Novo Designed Coiled-Coil Peptide with a Reversible pH-Induced Oligomerization Switch.

Protein conformational switches have many useful applications but are difficult to design rationally. Here we demonstrate how the isoenergetic energy landscape of higher-order coiled coils can enable the formation of an oligomerization switch by insertion of a single destabilizing element into an otherwise stable computationally designed scaffold. We describe a de novo designed peptide that was discovered to switch between a parallel symmetric pentamer at pH 8 and a trimer of antiparallel dimers at pH 6.

The Na+ transport in gram-positive bacteria defect in the Mrp antiporter complex measured with 23Na nuclear magnetic resonance.

(23)Na nuclear magnetic resonance (NMR) has previously been used to monitor Na(+) translocation across membranes in gram-negative bacteria and in various other organelles and liposomes using a membrane-impermeable shift reagent to resolve the signals resulting from internal and external Na(+). In this work, the (23)Na NMR method was adapted for measurements of internal Na(+) concentration in the gram-positive bacterium Bacillus subtilis, with the aim of assessing the Na(+) translocation activity of the Mrp (multiple resistance and pH) antiporter complex, a member of the cation proton antiporter-3 (CPA-3) family. The sodium-sensitive growth phenotype observed in a B.

Functional role of the MrpA- and MrpD-homologous protein subunits in enzyme complexes evolutionary related to respiratory chain complex I.

NADH:quinone oxidoreductase or complex I is a large membrane bound enzyme complex that has evolved from the combination of smaller functional building blocks. Intermediate size enzyme complexes exist in nature that comprise some, but not all of the protein subunits in full size 14-subunit complex I. The membrane spanning complex I subunits NuoL, NuoM and NuoN are homologous to each other and to two proteins from one particular class of Na(+)/H(+) antiporters, denoted MrpA and MrpD.

Use of (113)Cd NMR to probe the native metal binding sites in metalloproteins: an overview.

Our laboratories have actively published in this area for several years and the objective of this chapter is to present as comprehensive an overview as possible. Following a brief review of the basic principles associated with (113)Cd NMR methods, we will present the results from a thorough literature search for (113)Cd chemical shifts from metalloproteins. The updated (113)Cd chemical shift figure in this chapter will further illustrate the excellent correlation of the (113)Cd chemical shift with the nature of the coordinating ligands (N, O, S) and coordination number/geometry, reaffirming how this method can be used not only to identify the nature of the protein ligands in uncharacterized cases but also the dynamics at the metal binding site.

Complete high-density lipoproteins in nanoparticle corona.

In a biological environment, nanoparticles immediately become covered by an evolving corona of biomolecules, which gives a biological identity to the nanoparticle and determines its biological impact and fate. Previous efforts at describing the corona have concerned only its protein content. Here, for the first time, we show, using size exclusion chromatography, NMR, and pull-down experiments, that copolymer nanoparticles bind cholesterol, triglycerides and phospholipids from human plasma, and that the binding reaches saturation.

A model of the complex between human beta-microseminoprotein and CRISP-3 based on NMR data.

beta-Microseminoprotein (MSP), a 10kDa seminal plasma protein, forms a tight complex with cysteine-rich secretory protein 3 (CRISP-3) from granulocytes. The 3D structure of human MSP has been determined but there is as yet no 3D structure for CRISP-3. We have now studied the complex between human MSP and CRISP-3 with multidimensional NMR.

Incomplete lipid chain freezing of sonicated vesicular dispersions of double-tailed ionic surfactants.

Lipid freezing in dilute sonicated vesicular dispersions was studied using differential scanning calorimetry (DSC) and 1H NMR. For charged, anionic, or cationic lipids, approximately half of the lipids remain in a fluid state when cooled 20 degrees C below the main chain melting temperature. With a zwitterionic phospholipid, on the other hand, essentially no supercooling of the liquid state was observed.

Solution structures of human and porcine beta-microseminoprotein.

Beta-microseminoprotein (MSP) is a small cysteine-rich protein (molecular mass about 10 kDa) first isolated from human seminal plasma and later identified in several other organisms. The function of MSP is not known, but a recent study has shown MSP to bind CRISP-3, a protein present in neutrophilic granulocytes. The amino acid sequence is highly variable between species raising the question of the evolutionary conservation of the 3D structure.

Streptococcal M protein: structural studies of the hypervariable region, free and bound to human C4BP.

Streptococcus pyogenes is a Gram-positive bacterium that causes several diseases, including acute tonsillitis and toxic shock syndrome. The surface-localized M protein, which is the most extensively studied virulence factor of S. pyogenes, has an approximately 50-residue N-terminal hypervariable region (HVR) that plays a key role in the escape of the host immunity.

Solution structure of the Ca2+-Binding EGF3-4 pair from vitamin K-dependent protein S: identification of an unusual fold in EGF3.

Vitamin K-dependent protein S is a cofactor of activated protein C, a serine protease that regulates blood coagulation. Deficiency of protein S can cause venous thrombosis. Protein S has four EGF domains in tandem; domains 2-4 bind calcium with high affinity whereas domains 1-2 mediate interaction with activated protein C.

Subtle sequence differences in a tumour-associated peptide epitope translate into major changes in antigenicity.

Antigenicity, the ability to bind to members of repertoire of diverse immune receptors, is a concept that is poorly characterised with respect to its defining parameters. To learn more about its makeup, we have investigated the ability of two peptides with highly related sequences, derived from the tumour-associated antigen mucin-1, to recruit in vitro members from a large naïve repertoire of synthetic human antibody fragments. One of the peptides represents the epitope that is immunodominant in mice.

NMR structure determination of proteins supplemented by quantum chemical calculations: detailed structure of the Ca2+ sites in the EGF34 fragment of protein S.

We present and test two methods to use quantum chemical calculations to improve standard protein structure refinement by molecular dynamics simulations restrained to experimental NMR data. In the first, we replace the molecular mechanics force field (employed in standard refinement to supplement experimental data) for a site of interest by quantum chemical calculations. This way, we obtain an accurate description of the site, even if a molecular-mechanics force field does not exist for this site, or if there is little experimental information about the site.

Stereoselective binding of levosimendan to cardiac troponin C causes Ca2+-sensitization.

The effects of the Ca(2+) sensitizer levosimendan and that of its stereoisomer dextrosimendan on the cardiac contractile apparatus were studied using skinned fibers obtained from guinea pig hearts. Levosimendan was found to be more effective than dextrosimendan in this model. The respective concentrations of levosimendan and dextrosimendan at EC(50) were 0.

Interaction of levosimendan with cardiac troponin C in the presence of cardiac troponin I peptides.

The interaction between troponin C (TnC) and troponin I (TnI) is essential for the regulation of muscle contraction. There are several binding sites for TnI on TnC that are differentially occupied depending on the phase of the contraction/relaxation cycle. TnI and TnC interact in an antiparallel fashion with each other.

NMR solution structure of calerythrin, an EF-hand calcium-binding protein from Saccharopolyspora erythraea.

The structure of calerythrin, a prokaryotic 20 kDa calcium-binding protein has been determined by solution NMR spectroscopy. Distance, dihedral angle, J coupling, secondary chemical shift, residual dipolar coupling and radius of gyration restraints reveal four EF-hand motifs arranged in a compact globular structure. A tight turn in the middle of the amino acid sequence brings the two halves, each comprising a pair of EF-hands, close together.

Quaternary structure built from subunits combining NMR and small-angle x-ray scattering data.

A new principle in constructing molecular complexes from the known high-resolution domain structures joining data from NMR and small-angle x-ray scattering (SAXS) measurements is described. Structure of calmodulin in complex with trifluoperazine was built from N- and C-terminal domains oriented based on residual dipolar couplings measured by NMR in a dilute liquid crystal, and the overall shape of the complex was derived from SAXS data. The residual dipolar coupling data serves to reduce angular degrees of freedom, and the small-angle scattering data serves to confine the translational degrees of freedom.

Interaction of bovine coagulation factor X and its glutamic-acid-containing fragments with phospholipid membranes. A surface plasmon resonance study.

The interaction of blood coagulation factor X and its Gla-containing fragments with negatively charged phospholipid membranes composed of 25 mol% phosphatidylserine (PtdSer) and 75 mol% phosphatidylcholine (PtdCho) was studied by surface plasmon resonance. The binding to 100 mol% PtdCho membranes was negligible. The calcium dependence in the membrane binding was evaluated for intact bovine factor X (factor X) and the fragment containing the Gla-domain and the N-terminal EGF (epidermal growth factor)-like domain, Gla-EGFN, from factor X.

Differences in backbone dynamics of two homologous bacterial albumin-binding modules: implications for binding specificity and bacterial adaptation.

Proteins G and PAB are bacterial albumin-binding proteins expressed at the surface of group C and G streptococci and Peptostreptococcus magnus, respectively. Repeated albumin-binding domains, known as GA modules, are found in both proteins. The third GA module of protein G from the group G streptococcal strain G148 (G148-GA3) and the second GA module of protein PAB from P.

Structure, specificity, and mode of interaction for bacterial albumin-binding modules.

We have determined the solution structure of an albumin binding domain of protein G, a surface protein of group C and G streptococci. We find that it folds into a left handed three-helix bundle similar to the albumin binding domain of protein PAB from Peptostreptococcus magnus. The two domains share 59% sequence identity, are thermally very stable, and bind to the same site on human serum albumin.

Isolated hypervariable regions derived from streptococcal M proteins specifically bind human C4b-binding protein: implications for antigenic variation.

Antigenic variation in microbial surface proteins represents an apparent paradox, because the variable region must retain an important function, while exhibiting extensive immunological variability. We studied this problem for a group of streptococcal M proteins in which the approximately 50-residue hypervariable regions (HVRs) show essentially no residue identity but nevertheless bind the same ligand, the human complement regulator C4b-binding protein (C4BP). Synthetic peptides derived from different HVRs were found to retain the ability to bind C4BP, implying that the HVR corresponds to a distinct ligand-binding domain that can be studied in isolated form.

Characterization of apo and partially saturated states of calerythrin, an EF-hand protein from S. erythraea: a molten globule when deprived of Ca(2+).

Calerythrin, a four-EF-hand calcium-binding protein from Saccharopolyspora erythraea, exists in an equilibrium between ordered and less ordered states with slow exchange kinetics when deprived of Ca(2+) and at low temperatures, as observed by NMR. As the temperature is raised, signal dispersion in NMR spectra reduces, and intensity of near-UV CD bands decreases. Yet far-UV CD spectra indicate only a small decrease in the amount of secondary structure, and SAXS data show that no significant change occurs in the overall size and shape of the protein.