NMR
linked to PubMed where applicable.
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PESCADOR: The Peptide in Solution ConformAtionDatabase and Online ResourceJ. Biomolecular NMR 23: 85-102
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Solution structure of the main alpha-amylaseinhibitor from amaranth seedsEur. J. Biochem. 268 (8) 2379-2389.
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NMR sequential assignments and solution structure of chlorotoxin a small scorpion toxin that blocks chloridechannels.Biochemistry 34(1) 13-21
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Homo- and heteronuclear 2D NMR studies of the globular domain of histone H1: full assignment tertiary structure and comparison with the globular domain of histone H5Biochemistry 33 (37) 11079-11086
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T1 relaxation time of water from a molecular dynamics simulation.Mol. Phys. 80(6) 1469-1484
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Homo- and heteronuclear 2D NMR studies of the globular domain of histone H1: sequential assignment and secondary structure.Biochemistry 32(42) 11345-11351
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Transfer NOE study of the conformation of oxytocin bound to bovine neurophysin IBiochemistry 32(36) 9423-9434.
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1H-NMR studies of protein fragments insolution.Journal of Cellular Biochemistry (XXIIAnnual Keystone Symposia on Molecular & Cellular Biology Frontiersof NMR in Molecular Biology III) suppl. 17C 282
In recent years a large body of data has been obtained from Nuclear Magnetic Resonance and Circular Dichroism experiments on the influence of the amino acid sequence and various other parameters on the conformational state of peptides in solution. Interpreting the experimental data in terms of the conformational populations of the peptides remains a key problem, for which current solutions leave appreciable room for improvement. Considering that making this body of data available for surveys and analysis should be instrumental in tackling the problem, we undertook the development of Pescador: The 'PEptides in Solution ConformAtion Database: Online Resource'. Pescador contains data from NMR and CD spectroscopy on peptides in solution as well as information on the structural parameters derived from these data. It also features specialized Web-based tools for data deposition, and means for readily accessing the stored information for analysis purposes. To illustrate the use of the database in deriving information for the conformational analysis of peptides, we show how the alpha proton delta-values stored in Pescador and measured by NMR for different peptides in different laboratories can be used to derive a new set of 'random coil' chemical shift values. Firstly, we show these values to be very similar to those obtained experimentally for model peptides in water, and their variation with increasing Tri-Fluoro-Ethanol (TFE) concentration is similar to that reported for model peptides. We show, furthermore, that the chemical shift data in Pescador can be used to derive correction factors that take into account effects of neighboring residues. These correction factors compare favorably with those recently derived from a series of model GGXGG peptides (Schwarzinger et al., 2001). These encouraging results suggest that, as the quantity of NMR data on peptide deposited in Pescador increases, surveys of these data should be a valuable means of deriving key parameters for the analysis of peptide conformation.
The most abundant alpha-amylase inhibitor (AAI) present in the seeds of Amaranthus hypochondriacus, a variety of the Mexican crop plant amaranth, is the smallest polypeptide (32 residues) known to inhibit alpha-amylase activity of insect larvae while leaving that of mammals unaffected. In solution, 1H NMR reveals that AAI isolated from amaranth seeds adopts a major trans (70%) and minor cis (30%) conformation, resulting from slow cis-trans isomerization of the Val15-Pro16 peptide bond. Both solution structures have been determined using 2D 1H-NMR spectroscopy and XPLOR followed by restrained energy refinement in the consistent-valence force field. For the major isomer, a total of 563 distance restraints, including 55 medium-range and 173 long-range ones, were available from the NOESY spectra. This rather large number of constraints from a protein of such a small size results from a compact fold, imposed through three disulfide bridges arranged in a cysteine-knot motif. The structure of the minor cis isomer has also been determined using a smaller constraint set. It reveals a different backbone conformation in the Pro10-Pro20 segment, while preserving the overall global fold. The energy-refined ensemble of the major isomer, consisting of 20 low-energy conformers with an average backbone rmsd of 0.29 +/- 0.19 A and no violations larger than 0.4 A, represents a considerable improvement in precision over a previously reported and independently performed calculation on AAI obtained through solid-phase synthesis, which was determined with only half the number of medium-range and long-range restraints reported here, and featured the trans isomer only. The resulting differences in ensemble precision have been quantified locally and globally, indicating that, for regions of the backbone and a good fraction of the side chains, the conformation is better defined in the new solution structure. Structural comparison of the solution structure with the X-ray structure of the inhibitor when bound to its alpha-amylase target in Tenebrio molitor shows that the backbone conformation is only slightly adjusted on complexation, while that of the side chains involved in protein-protein contacts is similar to those present in solution. Therefore, the overall conformation of AAI appears to be predisposed to binding to its target alpha-amylase, confirming the view that it acts as a lid on top of the alpha-amylase active site.
The solution structure of chlorotoxin, a small toxin purified from the venom of the Leiurus quinquestriatus scorpion, has been determined using 2D 1H NMR spectroscopy. Analysis of the NMR data shows that the structure consists of a small three-stranded antiparallel beta-sheet packed against an alpha-helix, thereby adopting the same fold as charybdotoxin and other members of the short scorpion toxin family [Arseniev et al. (1984) FEBS Lett. 165, 57-62; Martins et al. (1990) FEBS Lett. 260, 249-253; Bontems et al. (1991) Science 254, 1521-1523]. Three disulfide bonds of chlorotoxin (Cys5-Cys28, Cys16-Cys33, and Cys20-Cys35), cross-linking the alpha-helix to the beta-sheet, follow the common pattern found in the other short scorpion toxins. The fourth disulfide bridge (Cys2-Cys19) links the small N-terminal beta strand to the rest of the molecule, in contrast to charybdotoxin where this disulfide bridge is absent and the first strand interacts with the rest of the molecule by several contacts between hydrophobic residues. Another structural difference between chlorotoxin and charybdotoxin is observed at the level of the alpha-beta turn. This difference is accompanied by a change in the electrostatic potential surface, which is largely positive at the level of this turn in chlorotoxin, whereas no such positive potential surface can be found at the same position in charybdotoxin. In the latter protein, the positive surface is formed by different charged residues situated on the solvent-exposed site of the C-terminal beta-sheet.(ABSTRACT TRUNCATED AT 250 WORDS)
The globular domain of chicken histone H1 (GH1) has been studied by 1H homonuclear and 1H-15N heteronuclear 2D NMR spectroscopy. After the full assignment of the proton and 15N resonances, the tertiary structure of GH1 was determined by an iterative procedure using distance geometry and restrained simulated annealing. The secondary structure elements of GH1, three helices (S5-A16, S24-A34, N42-K56) followed by a beta-hairpin (L59-L73), are folded in a manner very similar to the corresponding parts of the globular domain of chicken histone H5 (GH5) [Clore et al. (1987) EMBO J. 6, 1833-1842; Ramakrishnan et al. (1993) Nature 362, 219-223]. However, subtle differences are detected between the two structures and between the electrostatic potentials surrounding the molecules. The most important differences are located in the loop between the second and third helices, a region that could be responsible for the different affinity for DNA. The most positively charged regions are not found in exactly the same position in GH1 and GH5. Nevertheless, their location seems to agree with the model where nucleosome binding takes place through contact points located at one DNA terminus and close to the dyad axis of the nucleosome [Schwabe & Travers (1993) Curr. Biol. 3, 628-630].
A recombinant 75 amino acid polypeptide corresponding to the globular domain of the chicken histone H1 (GH1) has been studied by 1H homonuclear and 1H-15N heteronuclear 2D NMR spectroscopy. Sequential assignment of the backbone and beta-proton resonances has enabled us to determine the secondary structure of GH1. It was found to consist of three helical regions (T7-S17, L25-Y37, E40-K56) and probably a beta-hairpin (L59-L73). This structure is similar to the structure of the globular domain of histone H5 (GH5) obtained both by NMR spectroscopy [Zarbock et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7628-7632; Clore et al. (1987) EMBO J. 6, 1833-1842] and by X-ray crystallography [Ramakrishnan et al. (1993) Nature 362, 219-223]. The beta-hairpin as suggested for GH1 is also present in the X-ray structure of GH5 but has not been reported for the NMR structure of GH5.
This study reports the structure of the peptide hormone oxytocin bound to its carrier protein, neurophysin I, obtained by nuclear magnetic resonance techniques. At the pH value of 2.1 in our experiments, the ligand is in fast exchange with its carrier protein, allowing the use of transfer-NOE methods. The number of distance constraints for the peptide being limited, considerable attention has been paid to an accurate distance determination. The resulting accurate distance limits were used as input for a distance geometry calculation followed by a restrained molecular dynamics run. Convergence to a well-defined family of structures for oxytocin in its bound state was reached. Both the backbone and the side-chain conformations differ between the bound form and the crystal structure of free oxytocin [Wood, S. P., et al. (1986) Science 232, 633]. These differences, as well as other structural features of the bound form, are discussed in terms of interactions made with the carrier protein. Transfer-NOE experiments at low peptide protein ratios provide direct experimental evidence for contacts between the oxytocin Tyr2 residue and an aromatic residue of neurophysin. The resonance assignments of the aromatic groups [Whittaker, B. A., et al. (1985) Biochemistry 24, 2782] together with the recently published X-ray structure of the neurophysin II protein complexed with a dipeptide [Chen et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 4240] allow us to assign the aromatic signal on the protein to the neurophysin Phe22 residue.
