The Y145Stop prion protein (PrP23-144), which has been linked to the development of a heritable prionopathy in humans, is a valuable in vitro model for elucidating the structural and molecular basis of amyloid seeding specificities. Here we report the sequential backbone and side-chain 13C and 15N assignments of mouse and Syrian hamster PrP23-144 amyloid fibrils determined by using 2D and 3D magic-angle spinning solid-state NMR. The assigned chemical shifts were used to predict the secondary structures for the core regions of the mouse and Syrian hamster PrP23-144 amyloids, and the results compared to those for human PrP23-144 amyloid, which has previously been analyzed by solid-state NMR techniques. 相似文献
Ahnak is a ~?700 kDa polypeptide that was originally identified as a tumour-related nuclear phosphoprotein, but later recognized to play a variety of diverse physiological roles related to cell architecture and migration. A critical function of Ahnak is modulation of Ca2+ signaling in cardiomyocytes by interacting with the β subunit of the L-type Ca2+ channel (CaV1.2). Previous studies have identified the C-terminal region of Ahnak, designated as P3 and P4 domains, as a key mediator of its functional activity. We report here the nearly complete 1H, 13C and 15N backbone NMR chemical shift assignments of the 11 kDa C-terminal P4 domain of Ahnak. This study lays the foundations for future investigations of functional dynamics, structure determination and interaction site mapping of the CaV1.2-Ahnak complex. 相似文献
The linear analysis of chemical shifts (LACS) has provided a robust method for identifying and correcting 13C chemical shift referencing problems in data from protein NMR spectroscopy. Unlike other approaches, LACS does not require
prior knowledge of the three-dimensional structure or inference of the secondary structure of the protein. It also does not
require extensive assignment of the NMR data. We report here a way of extending the LACS approach to 15N NMR data from proteins, so as to enable the detection and correction of inconsistencies in chemical shift referencing for
this nucleus. The approach is based on our finding that the secondary 15N chemical shift of the backbone nitrogen atom of residue i is strongly correlated with the secondary chemical shift difference (experimental minus random coil) between the alpha and
beta carbons of residue i − 1. Thus once alpha and beta 13C chemical shifts are available (their difference is referencing error-free), the 15N referencing can be validated, and an appropriate offset correction can be derived. This approach can be implemented prior
to a structure determination and can be used to analyze potential referencing problems in database data not associated with
three-dimensional structure. Application of the LACS algorithm to the current BMRB protein chemical shift database, revealed
that nearly 35% of the BMRB entries have δ15N values mis-referenced by over 0.7 ppm and over 25% of them have δ1HN values mis-referenced by over 0.12 ppm. One implication of the findings reported here is that a backbone 15N chemical shift provides a better indicator of the conformation of the preceding residue than of the residue itself.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Carbonyl 13C′ relaxation is dominated by the contribution from the 13C′ chemical shift anisotropy (CSA). The relaxation rates provide useful and non-redundant structural information in addition
to dynamic parameters. It is straightforward to acquire, and offers complimentary structural information to the 15N relaxation data. Furthermore, the non-axial nature of the 13C′ CSA tensor results in a T1/T2 value that depends on an additional angular variable even when the diffusion tensor of the protein molecule is axially symmetric.
This dependence on an extra degree of freedom provides new geometrical information that is not available from the NH dipolar
relaxation. A protocol that incorporates such structural restraints into NMR structure calculation was developed within the
program Xplor-NIH. Its application was illustrated with the yeast Fis1 NMR structure. Refinement against the 13C′ T1/T2 improved the overall quality of the structure, as evaluated by cross-validation against the residual dipolar coupling as
well as the 15N relaxation data. In addition, possible variations of the CSA tensor were addressed.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Performance of 18 DFT functionals (B1B95, B3LYP, B3PW91, B97D, BHandHLYP, BMK, CAM-B3LYP, HSEh1PBE, M06-L, mPW1PW91, O3LYP, OLYP, OPBE, PBE1PBE, tHCTHhyb, TPSSh, wB97xD, VSXC) in combinations with six basis sets (cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, aug-cc-pVTZ, IGLO-II, and IGLO-III) and three methods for calculating magnetic shieldings (GIAO, CSGT, IGAIM) was tested for predicting 1H and 13C chemical shifts for 25 organic compounds, for altogether 86 H and 88 C atoms. Proton shifts varied between 1.03 ppm to 12.00 ppm and carbon shifts between 7.87 ppm to 209.28 ppm. It was found that the best method for calculating 13C shifts is PBE1PBE/aug-cc-pVDZ with CSGT or IGAIM approaches (mae?=?1.66 ppm), for 1H the best results were obtained with HSEh1PBE, mPW1PW91, PBE1PBE, CAM-B3LYP, and B3PW91 functionals with cc-pVTZ basis set and with CSGT or IGAIM approaches (mae?=?0.28 ppm). We found that often larger basis sets do not give better results for chemical shifts. The best basis sets for calculating 1H and 13C chemical shifts were cc-pVTZ and aug-cc-pVDZ, respectively. CSGT and IGAIM NMR approaches can perform really well and are in most cases better than popular GIAO approach.
Graphical Abstract Mean absolute errors for 1H and 13C chemical shifts and computational times of neutral toluene molecule with aug-cc-pVDZ basis set and CSGT approach
Thioredoxins (Trx) are ubiquitous proteins that regulate several biochemical processes inside the cell. Trx is an important player, displaying oxidoreductase activity and helping to keep and regulate the oxidative state of the cellular environment. Trx also participates in the regulation of many cellular functions, such as DNA synthesis, protection against oxidative stress, cell cycle and signal transduction. The oxidized Trx is the target for another set of proteins, such as thioredoxin reductase (TrR), which used the reductive potential of NADPH. The oxidized state of Trx also plays important role in regulation of redox state in the cells. In this regard, the oxidized form of Trx is a putative conformer that contributes to the cellular redox environment. Here we report the chemical shift assignments (1H, 13C and 15N) in solution at 15 °C. We also showed the secondary structure analysis of the oxidized form of yeast thioredoxin (yTrx1) as basis for future NMR studies of protein–target interactions and dynamics. The assignment was done at low concentration (200 µM) because it is important to keep intact the water cavity. 相似文献
13C-13C NOESY experiments were performed under long mixing time conditions on reduced human superoxide dismutase (32 kDa, 15N, 13C and 70% 2H labeled). 13C-13C couplings were successfully eliminated through post-processing of in-phase-anti-phase (IPAP) data. It appears that at mixing time m of 3.0 s the spin diffusion mechanism allows the detection of 96% of the two-bond correlations involving C and C. The interpretation was confirmed by simulations. This approach broadens the range of applicability of 13C-13C NOESY spectroscopy. 相似文献
Inconsistent 13C and 15N chemical shift referencing is a continuing problem associated with protein chemical shift assignments deposited in BioMagResBank (BMRB). Here we describe a simple and robust approach that can quantitatively determine the 13C and 15N referencing offsets solely from chemical shift assignment data and independently of 3D coordinate data. This novel structure-independent approach permitted the assessment and determination of 13C and 15N reference offsets for all protein entries deposited in the BMRB. Tests on 452 proteins with known 3D structures show that this structure-independent approach yields 13C and 15N referencing offsets that exhibit excellent agreement with those calculated on the basis of 3D structures. Furthermore, this protocol appears to improve the accuracy of chemical shift-derived secondary structural identification, and has been formally incorporated into a computer program called PSSI (http//www.pronmr.com).Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1007/s10858-004-7441-3 相似文献
Calcineurin (CaN) plays an important role in T-cell activation, cardiac system development and nervous system function. Previous studies have demonstrated that the regulatory domain (RD) of CaN binds calmodulin (CaM) towards the N-terminal end. Calcium-loaded CaM activates the serine/threonine phosphatase activity of CaN by binding to the RD, although the mechanistic details of this interaction remain unclear. It is thought that CaM binding at the RD displaces the auto-inhibitory domain (AID) from the active site of CaN, activating phosphatase activity. In the absence of calcium-loaded CaM, the RD is disordered, and binding of CaM induces folding in the RD. In order to provide mechanistic detail about the CaM–CaN interaction, we have undertaken an NMR study of the RD of CaN. Complete 13C, 15N and 1H assignments of the RD of CaN were obtained using solution NMR spectroscopy. The backbone of RD has been assigned using a combination of 13C-detected CON-IPAP experiments as well as traditional HNCO, HNCA, HNCOCA and HNCACB-based 3D NMR spectroscopy. A 15N-resolved TOCSY experiment has been used to assign Hα and Hβ chemical shifts. 相似文献
Human uracil N-glycosylase isoform 2—UNG2 consists of an N-terminal intrinsically disordered regulatory domain (UNG2 residues 1–92, 9.3 kDa) and a C-terminal structured catalytic domain (UNG2 residues 93–313, 25.1 kDa). Here, we report the backbone 1H, 13C, and 15N chemical shift assignment as well as secondary structure analysis of the N-and C-terminal domains of UNG2 representing the full-length UNG2 protein. 相似文献
Intramolecular correlations among the 18O-labels of metabolic oligophosphates, mapped by J-decoupled 31P NMR 2D chemical shift correlation spectroscopy, impart stringent constraints to the 18O-isotope distributions over the whole oligophosphate moiety. The multiple deduced correlations of isotopic labels enable
determination of site-specific fractional isotope enrichments and unravel the isotopologue statistics. This approach ensures
accurate determination of 18O-labeling rates of phosphometabolites, critical in biochemical energy conversion and metabolic flux transmission. The biological
usefulness of the J-decoupled 31P NMR 2D chemical shift correlation maps was validated on adenosine tri-phosphate fractionally 18O labeled in perfused mammalian hearts. 相似文献
Thirty-one proteins are known to form extracellular fibrillar amyloid in humans. Molecular information about many of these proteins in their monomeric, intermediate or fibrillar form and how they aggregate and interact to form the insoluble fibrils is sparse. This is because amyloid proteins are notoriously difficult to study in their soluble forms, due to their inherent propensity to aggregate. Using recent developments in fast NMR techniques, band-selective excitation short transient and band-selective optimized flip-angle short-transient heteronuclear multiple quantum coherence we have been able to assign a 5 kDa full-length amyloidogenic protein called medin. Medin is the key protein component of the most common form of localised amyloid with a proposed role in aortic aneurysm and dissection. This assignment will now enable the study of the early interactions that could influence initiation and progression of medin aggregation. The chemical shifts have been deposited in the BioMagRes-Bank accession Nos. 25399 and 26576. 相似文献
1H NMR complexation-induced changes in chemical shift (CIS) of HN protons have been used to characterize the complexes of barnase
with the deoxyoligonucleotides d(GC) and d(CGAC). Quantitative shift changes are used not only to locate the most probable
binding site (using ring-current shifts), but also to determine the orientation of the ligand within the binding site, based
on a more complete shift calculation including bond magnetic anisotropies and electric field effects. For both ligands, the
guanine is in the same binding site cleft, in the same position as identified in the crystal structure of the d(CGAC) complex.
By contrast, a previous X-ray crystal structure of the d(GC) complex showed the ligand in the mouth of the active site, rather
than at the guanyl-specific site, implying that the location may be an artifact of the crystallisation process. 相似文献
The major virulence factor of enterotoxigenic Escherichia coli is the heat-labile enterotoxin (LT), an AB5 toxin closely related to the cholera toxin. LT consists of six subunits, the catalytically active A-subunit and five B-subunits arranged as a pentameric ring (LTB), which enable the toxin to bind to the epithelial cells in the intestinal lumen. LTB has two recognized binding sites; the primary binding site is responsible for anchoring the toxin to its main receptor, the GM1-ganglioside, while the secondary binding site recognizes blood group antigens. Herein, we report the 1H, 13C, 15N main chain assignment of LTB from human isolates (hLTB; 103 a.a. per subunit, with a total molecular mass of 58.5 kDa). The secondary structure was predicted based on 13C′, 13Cα, 13Cβ, 1HN and 15N chemical shifts and compared to a published crystal structure of LTB. Neolactotetraose (NEO) was titrated to hLTB and chemical shift perturbations were measured. The chemical shift perturbations were mapped onto the crystal structure, confirming that NEO binds to the primary binding site of hLTB and competes with GM1-binding. Our new data further lend support to the hypothesis that binding at the primary binding site is transmitted to the secondary binding site of the toxin, where it may influence the binding to blood group antigens. 相似文献
K-Ras is a key driver of oncogenesis, accounting for approximately 80% of Ras-driven human cancers. The small GTPase cycles between an inactive, GDP-bound and an active, GTP-bound state, regulated by guanine nucleotide exchange factors and GTPase activating proteins, respectively. Activated K-Ras regulates cell proliferation, differentiation and survival by signaling through several effector pathways, including Raf-MAPK. Oncogenic mutations that impair the GTPase activity of K-Ras result in a hyperactivated state, leading to uncontrolled cellular proliferation and tumorogenesis. A cysteine mutation at glycine 12 is commonly found in K-Ras associated cancers, and has become a recent focus for therapeutic intervention. We report here 1HN, 15N, and 13C resonance assignments for the 19.3 kDa (aa 1–169) human K-Ras protein harboring an oncogenic G12C mutation in the GDP-bound form (K-RASG12C-GDP), using heteronuclear, multidimensional NMR spectroscopy. Backbone 1H–15N correlations have been assigned for all non-proline residues, except for the first methionine residue. 相似文献
The conformational dependence of 13C chemical shift values of RNA riboses determined by liquid-state NMR spectroscopy was evaluated using data deposited for
RNA structures in the RCSD and BMRB data bases. Results derived support the applicability of the canonical coordinates approach
of Rossi and Harbison (J Magn Reson 151:1–8, 2001) in liquid-state NMR to assess the sugar pucker of ribose units in RNA.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
High resolution 13C-detected solid-state NMR spectra of the deuterated beta-1 immunoglobulin binding domain of the protein G (GB1) have been
collected to show that all 15N, 13C′, 13Cα and 13Cβ sites are resolved in 13C–13C and 15N–13C spectra, with significant improvement in T2 relaxation times and resolution at high magnetic field (750 MHz). The comparison of echo T2 values between deuterated and protonated GB1 at various spinning rates and under different decoupling schemes indicates that
13Cα T2′ times increase by almost a factor of two upon deuteration at all spinning rates and under moderate decoupling strength,
and thus the deuteration enables application of scalar-based correlation experiments that are challenging from the standpoint
of transverse relaxation, with moderate proton decoupling. Additionally, deuteration in large proteins is a useful strategy
to selectively detect polar residues that are often important for protein function and protein–protein interactions. 相似文献