scholarly journals Measuring transverse relaxation in highly paramagnetic systems

2020 ◽  
Vol 74 (8-9) ◽  
pp. 431-442
Author(s):  
Michele Invernici ◽  
Inês B. Trindade ◽  
Francesca Cantini ◽  
Ricardo O. Louro ◽  
Mario Piccioli
Keyword(s):  
Structural Biology ◽  
Paramagnetic Center ◽  
Metal Ion ◽  
Biological Function ◽  
Nuclear Relaxation ◽  
The Novel ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Powerful Source ◽  
Ca 50

Abstract The enhancement of nuclear relaxation rates due to the interaction with a paramagnetic center (known as Paramagnetic Relaxation Enhancement) is a powerful source of structural and dynamics information, widely used in structural biology. However, many signals affected by the hyperfine interaction relax faster than the evolution periods of common NMR experiments and therefore they are broadened beyond detection. This gives rise to a so-called blind sphere around the paramagnetic center, which is a major limitation in the use of PREs. Reducing the blind sphere is extremely important in paramagnetic metalloproteins. The identification, characterization, and proper structural restraining of the first coordination sphere of the metal ion(s) and its immediate neighboring regions is key to understand their biological function. The novel HSQC scheme we propose here, that we termed R2-weighted, HSQC-AP, achieves this aim by detecting signals that escaped detection in a conventional HSQC experiment and provides fully reliable R2 values in the range of 1H R2 rates ca. 50–400 s−1. Independently on the type of paramagnetic center and on the size of the molecule, this experiment decreases the radius of the blind sphere and increases the number of detectable PREs. Here, we report the validation of this approach for the case of PioC, a small protein containing a high potential 4Fe-4S cluster in the reduced [Fe4S4]2+ form. The blind sphere was contracted to a minimal extent, enabling the measurement of R2 rates for the cluster coordinating residues.

The influence of manganese(II) and copper(II) on 13C nuclear relaxation rates in imidazole

1976 ◽  
Vol 54 (4) ◽  
pp. 617-623 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Moira R. Graham
Keyword(s):  
Aqueous Solutions ◽  
Line Width ◽  
Important Influence ◽  
Nuclear Relaxation ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Width Measurements

13C nuclear relaxation rates have been measured for aqueous solutions of imidazole at 31 °C for several values of pH. The influence of Mn(II) and Cu(II) on these relaxation rates has been examined. The results indicate that 13C transverse relaxation rates of imidazole in the presence of these metals are completely dominated by the scalar mechanism. Because of the important influence of this mechanism it is not possible to obtain the geometry of complexes between imidazole-like ligands and Mn(II) or Cu(II) from 13C line-width measurements.

63,65Cu NMR and NQR in YBa2Cu3O7-δ

1987 ◽  
Vol 99 ◽  
Author(s):  
W. W. Warren ◽  
R. E. Walstedt ◽  
R. F. Bell ◽  
G. F. Brennert ◽  
R. J. Cava ◽  
...  
Keyword(s):  
Superconducting State ◽  
High Field ◽  
Nuclear Relaxation ◽  
Relaxation Rates ◽  
Structural Units ◽  
Nmr Spectrum ◽  
Electron Pairing

ABSTRACTNMR and NQR results are reported for 63,65Cu in YBa2Cu3O7-δ. Analysis of the high-field NMR spectrum indicates substantial disorder in the copper-oxygen planes. Nuclear relaxation rates are significantly different for copper in the chains and planes both above and below Tc and yield sharply different electron pairing energies on these structural units in the superconducting state.

scholarly journals Molecular Characterization of TEM-59 (IRT-17), a Novel Inhibitor-Resistant TEM-Derived β-Lactamase in a Clinical Isolate of Klebsiella oxytoca

1999 ◽  
Vol 43 (7) ◽  
pp. 1657-1661 ◽  
Author(s):  
H. Bermudes ◽  
F. Jude ◽  
E. B. Chaibi ◽  
C. Arpin ◽  
C. Bebear ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Amino Acid Change ◽  
Klebsiella Oxytoca ◽  
Conjugative Plasmid ◽  
Hydrolysis Rate ◽  
Nucleotide Sequence Analysis ◽  
The Novel ◽  
Ca 50 ◽  
Level Resistance

ABSTRACT A clinical isolate of Klebsiella oxytoca (Kox 443) was found to have a low-level resistance to broad-spectrum penicillins (MICs of amoxicillin and ticarcillin, 256 and 32 μg/ml, respectively), without substantial potentiation by 2 μg of clavulanic acid per ml (amoxicillin- and ticarcillin-clavulanate, 128 and 8 μg/ml, respectively), while being fully susceptible to cephalosporins and other β-lactam antibiotics. These resistances were carried by a ca. 50-kb conjugative plasmid that encodes a single β-lactamase with a pI of 5.6. Compared to TEM-2, this enzyme exhibited a 3- to 30-fold higher Km and a decreased maximal hydrolysis rate for β-lactams; higher concentrations of suicide inactivators (5- to 500-fold higher concentrations giving a 50% reduction in hydrolysis) were required for inhibition. Nucleotide sequence analysis revealed identity between the bla TEM gene of Kox 443 and the bla TEM-2 gene, except for a single A-to-G change at position 590, leading to the amino acid change from Ser-130 Gly. This mutation has not been reported previously in the TEM type β-lactamases produced by clinical strains, and the novel enzyme was called TEM-59 (alternative name IRT-17). This is the first description of an inhibitor-resistant TEM-derived enzyme in the speciesK. oxytoca.

Copper(II) and zinc(II) dinuclear enzymes model compounds: The nature of the metal ion in the biological function

2017 ◽  
Vol 1150 ◽  
pp. 316-328 ◽  
Author(s):  
L.G. Ferraresso ◽  
E.G.R. de Arruda ◽  
T.P.L. de Moraes ◽  
R.B. Fazzi ◽  
A.M. Da Costa Ferreira ◽  
...  
Keyword(s):  
Metal Ion ◽  
Biological Function ◽  
Model Compounds

scholarly journals Identification by RNA Profiling and Mutational Analysis of the Novel Copper Resistance Determinants CrdA (HP1326), CrdB (HP1327), and CzcB (HP1328) in Helicobacter pylori

2002 ◽  
Vol 184 (23) ◽  
pp. 6700-6708 ◽  
Author(s):  
Barbara Waidner ◽  
Klaus Melchers ◽  
Igor Ivanov ◽  
Hannes Loferer ◽  
Klaus W. Bensch ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Metal Ion ◽  
Specific Protein ◽  
Copper Resistance ◽  
System Component ◽  
The Novel ◽  
Rna Profiling ◽  
Metal Ion Homeostasis ◽  
Resistance Determinants ◽  
H Pylori

ABSTRACT Mechanisms involved in maintaining cytoplasmic metal ion homeostasis play a central role in the adaptation of Helicobacter pylori to the changing gastric environment. An investigation of the global regulatory responses to copper ions by using RNA profiling with a threshold factor of 4.0 revealed that copper induces transcription of 19 H. pylori genes and that only the ferritin gene pfr is repressed. The 57-fold copper induction identified the HP1326 gene encoding an H. pylori-specific protein as a candidate for a novel copper resistance determinant. The HP1326 gene is expressed as a monocistronic unit, and two small HP1326 mRNAs are copper induced. The HP1326 protein is secreted and is required for copper resistance maintained by cytoplasmic copper homeostasis, as H. pylori HP1326 mutants were copper sensitive and displayed increased copper induction of HP1326 transcription as well as elevated copper repression of ferritin synthesis. The clear copper-sensitive phenotype displayed by H. pylori HP1327 and HP1328 mutants provides strong evidence that the HP1326 protein, together with the signal peptide site of the H. pylori-specific protein HP1327, whose gene is located downstream from that encoding HP1326, and the CzcB and CzcA metal efflux system component homologs HP1328 and HP1329, constitutes a novel type of copper efflux pump, as discussed below. The HP1329 gene could not be inactivated, but the 14-fold transcriptional copper induction determined by RNA profiling points towards a function of the encoded CzcA homolog in copper resistance. In summary, results from RNA profiling identified the novel H. pylori-specific copper resistance determinants CrdA (HP1326) and CrdB (HP1327), which are required for adaptation to copper-rich environmental conditions.

scholarly journals The novel ECF56 SigG1-RsfG system modulates morphological differentiation and metal-ion homeostasis in Streptomyces tsukubaensis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rute Oliveira ◽  
Matthew J. Bush ◽  
Sílvia Pires ◽  
Govind Chandra ◽  
Delia Casas-Pastor ◽  
...  
Keyword(s):  
Metal Ion ◽  
Ion Homeostasis ◽  
Morphological Differentiation ◽  
The Novel ◽  
Copper Trafficking ◽  
Streptomyces Tsukubaensis ◽  
Metal Ion Homeostasis ◽  
Σ Factor ◽  
Domain Organisation

AbstractExtracytoplasmic function (ECF) sigma factors are key transcriptional regulators that prokaryotes have evolved to respond to environmental challenges. Streptomyces tsukubaensis harbours 42 ECFs to reprogram stress-responsive gene expression. Among them, SigG1 features a minimal conserved ECF σ2–σ4 architecture and an additional C-terminal extension that encodes a SnoaL_2 domain, which is characteristic for ECF σ factors of group ECF56. Although proteins with such domain organisation are widely found among Actinobacteria, the functional role of ECFs with a fused SnoaL_2 domain remains unknown. Our results show that in addition to predicted self-regulatory intramolecular amino acid interactions between the SnoaL_2 domain and the ECF core, SigG1 activity is controlled by the cognate anti-sigma protein RsfG, encoded by a co-transcribed sigG1-neighbouring gene. Characterisation of ∆sigG1 and ∆rsfG strains combined with RNA-seq and ChIP-seq experiments, suggests the involvement of SigG1 in the morphological differentiation programme of S. tsukubaensis. SigG1 regulates the expression of alanine dehydrogenase, ald and the WhiB-like regulator, wblC required for differentiation, in addition to iron and copper trafficking systems. Overall, our work establishes a model in which the activity of a σ factor of group ECF56, regulates morphogenesis and metal-ions homeostasis during development to ensure the timely progression of multicellular differentiation.

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