1H, 13C and 15N chemical shift referencing in biomolecular NMR

Summary A considerable degree of variability exists in the way that ¹H, ¹³C and ¹⁵N chemical shifts are reported and referenced for biomolecules. In this article we explore some of the reasons for this situation and propose guidelines for future chemical shift referencing and for conversion from many common ¹H, ¹³C and ¹⁵N chemical shift standards, now used in biomolecular NMR, to those proposed here.Abbreviations TMS tetramethylsilane - TSP 3-(trimethylsilyl)-propionate, sodium salt - DSS 2,2-dimethyl-2-silapentane-5-sulfonate, sodium salt - TFE 2,2,2-trifluoroethanol - DMSO dimethyl sulfoxide     

Backbone and sidechain 1H, 13C and 15N chemical shift assignments of the hydrophobin DewA from Aspergillus nidulans

Hydrophobins are proteins secreted by filamentous fungi that are able to self-assemble into monolayers at hydrophobic:hydrophilic interfaces. The layers are amphipathic and can reverse the wettability of surfaces. Hydrophobins have several roles in fungal development, including the formation of coatings on fungal structures to render them hydrophobic. Here we report the backbone and sidechain assignments for the class I hydrophobin DewA from the fungus Aspergillus nidulans.     

Backbone 1H, 15N, and 13C resonance assignment of HP1242 from Helicobacter pylori

One of the small proteins from Helicobacter pylori, HP1242, was investigated by the solution nuclear magnetic resonance (NMR) spectroscopy. HP1242 is known as a 76-residue conserved hypothetical protein and its function cannot be identified based on sequence homology. Here, the results of the backbone (1)H, (15)N, and (13)C resonance assignments of the HP1242 are reported using double- and triple-resonance techniques. About 95 % of all of the (1)HN, (15)N, (13)CO, (13)Calpha, and (13)Cbeta resonances that cover 75 non-Proline residues of the 76 residues are clarified through sequential- and specific- assignments. In addition, three helical regions were clearly identified on the basis of the resonance assignments.     

1H, 13C, and 15N chemical shift assignments of ZCCHC9

ZCCHC9 is a human nuclear protein with sequence homology to yeast Air1p/Air2p proteins which are RNA-binding subunits of the Trf4/Air2/Mtr4 polyadenylation (TRAMP) complex involved in nuclear RNA quality control and degradation in yeast. The ZCCHC9 protein contains four retroviral-type zinc knuckle motifs. Here, we report the NMR spectral assignment of the zinc knuckle region of ZCCHC9. These data will allow performing NMR structural and RNA-binding studies of ZCCHC9 with the aim to investigate its role in the RNA quality control in human.     

1H, 13C, and 15N backbone and side-chain chemical shift assignment of the staphylococcal MazF mRNA interferase

MazF proteins are ribonucleases that cleave mRNA with high sequence-specificity as part of bacterial stress response and that are neutralized by the action of the corresponding antitoxin MazE. Prolonged activation of the toxin MazF leads to cell death. Several mazEF modules from Gram-negative bacteria have been characterized in terms of catalytic activity, auto-regulation mechanism and structure, but less is known about their distant relatives found in Gram-positive organisms. Currently, no solution NMR structure is available for any wild-type MazF toxin. Here we report the ¹H, ¹⁵N and ¹³C backbone and side-chain chemical shift assignments of this toxin from the pathogen bacterium Staphylococcus aureus. The BMRB accession number is 17288.     

Backbone and side-chain 1H, 15N, and 13C resonance assignments of Norwalk virus protease

Norovirus protease cleaves the virus-encoded polyprotein into six mature nonstructural proteins, presenting itself as an essential enzyme for the viral replication as well as an attractive target for the antiviral drug development. A deeper understanding of the structural mechanism of the protease-substrates/inhibitors interactions by means of solution NMR methods would facilitate a rational design of the virus protease inhibitor. We here report the backbone and side-chain resonance assignment of the protease from Norwalk virus, which is the prototype strain of norovirus. The assignment data has been deposited in the BMRB database under the accession number 17523.     

1H, 15N and 13C backbone chemical shift assignment of the titin A67-A68 domain tandem

Single molecules of the giant protein titin extend across half of the muscle sarcomere, from the Z-line to the M-line, and have roles in muscle assembly and elasticity. In the A-band titin is attached to thick filaments and here the domain arrangement occurs in regular patterns of eleven called the large super-repeat. The large super-repeat itself occurs eleven times and forms nearly half the titin molecule. Interactions of the large super-repeats with myosin are consistent with a role in thick filament assembly. Here we report backbone assignments of the titin A67-A68 domain tandem (Fn-Ig) from the third super-repeat (A65-A75) completed using triple resonance NMR experiments.     

1H, 13C and 15N chemical shift assignments of Ninjurin1 Extracellular N-terminal Domain

Cell adhesion molecules play a crucial role in fundamental biological processes via regulating cell–cell interactions. Nerve injury induced protein1 (Ninjurin1) is a novel adhesion protein that has no significant homology with other known cell adhesion molecules. Here we present the assignment of an 81 aa construct for human Ninjurin1 Extracellular N-Terminal (ENT) domain, which comprises the critical adhesion domain.     

1H, 15N,and 13C chemical shift assignments of murine calcium-binding protein 4

Calcium-binding protein 4 (CaBP4) regulates voltage-gated Ca²⁺ channels in retinal rod cells and specific mutations within CaBP4 are associated with congenital stationary night blindness type 2. We report complete NMR chemical shift assignments of the Ca²⁺-saturated form of CaBP4 with Ca²⁺ bound at EF1, EF3 and EF4 (BMRB no. 18877).     

13C, 15N and 1H backbone and side chain chemical shift assignment of acid-stress bacterial chaperone HdeA at pH 6

HdeA is a small chaperone found in the periplasm of several common pathogenic bacteria (Escherichia coli, Shigella flexneri and Brucella abortus) which are the leading causes of dysentery worldwide, especially in developing countries. Its job is to protect other periplasmic proteins from aggregating as the bacteria pass through the low pH environment of the human stomach on their way to infect the intestines. HdeA is an inactive folded dimer at neutral pH, but becomes a disordered active monomer at pH < 3. To initiate NMR characterization of HdeA at pH 6, 94 % of the backbone and 86 % of the side chain chemical shifts have been assigned. The loop linking helices B and C remains largely unassigned due to missing peaks in the ¹H–¹⁵N HSQC and other spectra, most likely due to intermediate timescale chemical exchange. Many of the weakest intensity backbone peaks correspond to residues that surround this loop within the tertiary structure. Assignment experiments have therefore helped to provide preliminary clues about the region of the protein that may be most responsible for initiating unfolding as the pH drops, and constitute an important first step in improving our understanding of, and ultimately combatting, HdeA activity.     

1H, 13C and 15N backbone and side-chain chemical shift assignments for oxidized and reduced desulfothioredoxin

Based on sequence homology, desulfothioredoxin (DTrx) from Desulfovibrio vulgaris Hildenborough has been identified as a new member of the thioredoxin superfamily. Desulfothioredoxin (104 amino acids) contains a particular active site consensus sequence, CPHC probably correlated to the anaerobic metabolism of these bacteria. We report the full ¹H, ¹³C and ¹⁵N resonance assignments of the reduced and the oxidized form of desulfothioredoxin (DTrx). 2D and 3D heteronuclear NMR experiments were performed using uniformly ¹⁵N-, ¹³C-labelled DTrx. More than 98% backbone and 96% side-chain ¹H, ¹³C and ¹⁵N resonance assignments were obtained. (BMRB deposits with accession number 16712 and 16713).     

1H, 15N, and 13C chemical shift assignments of calcium-binding protein 1 (CaBP1)

Calcium-binding protein 1 (CaBP1) regulates inositol 1,4,5-trisphosphate receptors (InsP₃Rs) and a variety of voltage-gated Ca²⁺ channels in the brain. We report complete NMR chemical shift assignments of Ca²⁺-free CaBP1 (residues 1–167, BMRB no. 15197).