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Federica Castellani

Publications and source records attributed to Federica Castellani.

14 recordsLinked to original sources
PubMed2005

Solid-state magic-angle spinning NMR of outer-membrane protein G from Escherichia coli.

Uniformly 13C-,15N-labelled outer-membrane protein G (OmpG) from Escherichia coli was expressed for structural studies by solid-state magic-angle spinning (MAS) NMR. Inclusion bodies of the recombinant, labelled protein were purified under denaturing conditions and refolded in detergent. OmpG was reconstituted into lipid bilayers and several milligrams of two-dimensional crystals were obtained. Solid-state MAS NMR spectra showed signals with an apparent line width of 80-120 Hz (including homonuclear scalar couplings). Signal patterns for several amino acids, including threonines, prolines and serines were resolved and identified in 2D proton-driven spin-diffusion (PDSD) spectra.

Bacterial Outer Membrane Proteins↗
PubMed2004

Towards structure determination of neurotoxin II bound to nicotinic acetylcholine receptor: a solid-state NMR approach.

Solid-state magic-angle spinning nuclear magnetic resonance (NMR) has sufficient resolving power for full assignment of resonances and structure determination of immobilised biological samples as was recently shown for a small microcrystalline protein. In this work, we show that highly resolved spectra may be obtained from a system composed of a receptor-toxin complex. The NMR sample used for our studies consists of a membrane preparation of the nicotinic acetylcholine receptor from the electric organ of Torpedo californica which was incubated with uniformly 13C-,15N-labelled neurotoxin II. Despite the large size of the ligand-receptor complex ( > 290 kDa) and the high lipid content of the sample, we were able to detect and identify residues from the ligand. The comparison with solution NMR data of the free toxin indicates that its overall structure is very similar when bound to the receptor, but significant changes were observed for one isoleucine.

Animals↗
PubMed2003

Determination of solid-state NMR structures of proteins by means of three-dimensional 15N-13C-13C dipolar correlation spectroscopy and chemical shift analysis.

In this paper, a three-dimensional (3D) NMR-based approach for the determination of the fold of moderately sized proteins by solid-state magic-angle spinning (MAS) NMR is presented and applied to the alpha-spectrin SH3 domain. This methodology includes the measurement of multiple (13)C-(13)C distance restraints on biosynthetically site-directed (13)C-enriched samples, obtained by growing bacteria on [2-(13)C]glycerol and [1,3-(13)C]glycerol. 3D (15)N-(13)C-(13)C dipolar correlation experiments were applied to resolve overlap of signals, in particular in the region where backbone carbon-carbon correlations of the C(alpha)-C(alpha), CO-CO, C(alpha)-CO, and CO-C(alpha) type appear. Additional restraints for confining the structure were obtained from phi and psi backbone torsion angles of 29 residues derived from C(alpha), C(beta), CO, NH, and H(alpha) chemical shifts. Using both distance and angular restraints, a refined structure was calculated with a backbone root-mean-square deviation of 0.7 A with respect to the average structure.

Carbon Isotopes↗
PubMed2003

1H detection in MAS solid-state NMR spectroscopy of biomacromolecules employing pulsed field gradients for residual solvent suppression.

In this communication, we demonstrate the feasibility of 1H detection in MAS solid-state NMR for a microcrystalline, uniformly 2H,15N-labeled sample of a SH3 domain of chicken alpha-spectrin, using pulsed field gradients for suppression of water magnetization. Today, B0 gradients are employed routinely in solution-state NMR for coherence order selection and solvent suppression. We suggest to use gradients to purge water magnetization which cannot be suppressed using conventional water suppression schemes. The achievable gain in sensitivity for 1H detection is in the order of 5 compared to the 15N detected version of the experiment (at a MAS rotation frequency of 13.5 kHz). We expect that this labeling concept which achieves high sensitivity due to 1H detection, in combination with the possibility to measure long range 1H-1H distances as we have shown previously, to be a useful tool for the determination of protein structures in the solid state.

Animals↗
PubMed2003

Characterization of (1)H-(1)H distances in a uniformly (2)H,(15)N-labeled SH3 domain by MAS solid-state NMR spectroscopy (section sign).

In this communication, we demonstrate the feasibility of obtaining long-range (1)H-(1)H distance information by MAS solid-state NMR for a microcrystalline, uniformly (2)H,(15)N-labeled sample of a SH3 domain of chicken alpha-spectrin. The experiments yield NOESY-type spectra and rely on the favorable dispersion of the (15)N chemical shifts of the protein backbone. Perdeuteration of nonexchangeable sites is employed to simplify proton spin systems and to obtain multiple structural information. Two mixing schemes, (1)H-(1)H double quantum filtered Post-C7 and (1)H spin diffusion, are implemented to obtain quantitative (1)H-(1)H distance information. Post-C7 and spin diffusion cross-peak buildup rates are discussed for initial-rate fitting and in the framework of n = 0 rotational resonance (rotor driven spin diffusion), respectively. Different deuteration schemes were tested to find conditions where short-range (1)H-(1)H interactions are truncated (e.g., between H(N) and H(alpha)), but long-range interactions are retained (e.g., between H(N) and H(N)).

Animals↗
PubMed2003

Assignment of amide proton signals by combined evaluation of HN, NN and HNCA MAS-NMR correlation spectra.

In this paper, we present a strategy for the (1)H(N) resonance assignment in solid-state magic-angle spinning (MAS) NMR, using the alpha-spectrin SH3 domain as an example. A novel 3D triple resonance experiment is presented that yields intraresidue H(N)-N-C(alpha) correlations, which was essential for the proton assignment. For the observable residues, 52 out of the 54 amide proton resonances were assigned from 2D ((1)H-(15)N) and 3D ((1)H-(15)N-(13)C) heteronuclear correlation spectra. It is demonstrated that proton-driven spin diffusion (PDSD) experiments recorded with long mixing times (4 s) are helpful for confirming the assignment of the protein backbone (15)N resonances and as an aid in the amide proton assignment.

Amides↗
PubMed2002

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy.

The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete (13)C and (15)N resonance assignments for a micro-crystalline preparation of the alpha-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-(13)C]glycerol or [2-(13)C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to approximately 7 A. The calculated global fold of the alpha-spectrin SH3 domain is based on 286 inter-residue (13)C-(13)C and six (15)N-(15)N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

Animals↗