1bh4
From Proteopedia
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==Overview== | ==Overview== | ||
| - | The three-dimensional solution structure of circulin A, a 30 residue | + | The three-dimensional solution structure of circulin A, a 30 residue polypeptide from the African plant Chassalia parvifolia, has been determined using two-dimensional 1H-NMR spectroscopy. Circulin A was originally identified based upon its inhibition of the cytopathic effects and replication of the human immunodeficiency virus. Structural restraints consisting of 369 interproton distances inferred from nuclear Overhauser effects, and 21 backbone dihedral and nine chi1 angle restraints from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimisation in the program X-PLOR. The final set of 12 structures had mean pairwise rms differences over the whole molecule of 0.91 A for the backbone atom, and 1.68 A for all heavy atoms. For the well-defined region encompassing residues 2-12 and 18-27, the corresponding values were 0.71 and 1.66 A, respectively. Circulin A adopts a compact structure consisting of beta-turns and a distorted segment of triple-stranded beta-sheet. Fluorescence spectroscopy provided additional evidence for a solvent-exposed Trp residue. The molecule is stabilised by three disulfide bonds, two of which form an embedded loop completed by the backbone fragments connecting the cysteine residues. A third disulfide bond threads through the centre of this loop to form a "cystine-knot" motif. This motif is present in a range of other biologically active proteins, including omega-contoxin GVIA and Cucurbita maxima trypsin inhibitor. Circulin A belongs to a novel class of macrocyclic peptides which have been isolated from plants in the Rubiaceae family. The global fold of circulin A is similar to kalata B1, the only member of this class for which a structure has previously been determined. |
==About this Structure== | ==About this Structure== | ||
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[[Category: Chassalia parviflora]] | [[Category: Chassalia parviflora]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Craik, D | + | [[Category: Craik, D J.]] |
| - | [[Category: Daly, N | + | [[Category: Daly, N L.]] |
[[Category: Koltay, A.]] | [[Category: Koltay, A.]] | ||
[[Category: anti-hiv activity]] | [[Category: anti-hiv activity]] | ||
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[[Category: cystine knot]] | [[Category: cystine knot]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:55:18 2008'' |
Revision as of 09:55, 21 February 2008
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CIRCULIN A FROM CHASSALIA PARVIFLORA, NMR, 12 STRUCTURES
Overview
The three-dimensional solution structure of circulin A, a 30 residue polypeptide from the African plant Chassalia parvifolia, has been determined using two-dimensional 1H-NMR spectroscopy. Circulin A was originally identified based upon its inhibition of the cytopathic effects and replication of the human immunodeficiency virus. Structural restraints consisting of 369 interproton distances inferred from nuclear Overhauser effects, and 21 backbone dihedral and nine chi1 angle restraints from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimisation in the program X-PLOR. The final set of 12 structures had mean pairwise rms differences over the whole molecule of 0.91 A for the backbone atom, and 1.68 A for all heavy atoms. For the well-defined region encompassing residues 2-12 and 18-27, the corresponding values were 0.71 and 1.66 A, respectively. Circulin A adopts a compact structure consisting of beta-turns and a distorted segment of triple-stranded beta-sheet. Fluorescence spectroscopy provided additional evidence for a solvent-exposed Trp residue. The molecule is stabilised by three disulfide bonds, two of which form an embedded loop completed by the backbone fragments connecting the cysteine residues. A third disulfide bond threads through the centre of this loop to form a "cystine-knot" motif. This motif is present in a range of other biologically active proteins, including omega-contoxin GVIA and Cucurbita maxima trypsin inhibitor. Circulin A belongs to a novel class of macrocyclic peptides which have been isolated from plants in the Rubiaceae family. The global fold of circulin A is similar to kalata B1, the only member of this class for which a structure has previously been determined.
About this Structure
1BH4 is a Single protein structure of sequence from Chassalia parviflora. Full crystallographic information is available from OCA.
Reference
Solution structure by NMR of circulin A: a macrocyclic knotted peptide having anti-HIV activity., Daly NL, Koltay A, Gustafson KR, Boyd MR, Casas-Finet JR, Craik DJ, J Mol Biol. 1999 Jan 8;285(1):333-45. PMID:9878410
Page seeded by OCA on Thu Feb 21 11:55:18 2008
