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PDBsum entry 1ad7
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Gamma-carboxyglutamic acid
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PDB id
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1ad7
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References listed in PDB file
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Key reference
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Title
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Three-Dimensional structure of a gamma-Carboxyglutamic acid-Containing conotoxin, Conantokin g, From the marine snail conus geographus: the metal-Free conformer.
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Authors
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A.C.Rigby,
J.D.Baleja,
B.C.Furie,
B.Furie.
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Ref.
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Biochemistry, 1997,
36,
6906-6914.
[DOI no: ]
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PubMed id
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Abstract
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Conantokin G is a gamma-carboxyglutamic acid-containing conotoxin from the venom
of the marine cone snail Conus geographus. The 17-residue peptide, which
contains five gamma-carboxyglutamic acid (Gla) residues and an amidated
C-terminal asparagine amide, was synthesized chemically in a form identical to
the natural conantokin G. To gain insight into the role of gamma-carboxyglutamic
acid in the structure of this peptide, we determined the three-dimensional
structure of conantokin G by 1H NMR and compared its structure to other
conotoxins and to the gamma-carboxyglutamic acid-containing regions of the
vitamin K-dependent blood-clotting proteins. Complete resonance assignments were
made by two-dimensional 1H NMR spectroscopy in the absence of metal ions. NOE
cross-peaks d(alphaN), d(NN), and d(betaN) provided interproton distance
information, and vicinal spin-spin coupling constants 3J(HN alpha) were used to
calculate phi torsion angles. Distance geometry and simulated annealing methods
were used to derive 20 convergent structures from a set of 227 interproton
distance restraints and 13 torsion angle measurements. The backbone rmsd to the
geometric average for 20 final structures is 0.8 +/- 0.1 A. Conantokin G
consists of a structured region commencing at Gla 3 and extending through
arginine 13. This structure includes a partial loop centered around Gla 3 and
Gla 4, a distorted type I turn between glutamine 6 and glutamine 9, and two type
I turns involving Gla 10, leucine 11, and isoleucine 12 and arginine 13.
Together, these two turns define approximately 1.6 turns of a distorted 3(10)
helix. The observed structure possesses structural elements similar to those
seen in the disulfide-linked conotoxins.
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