1qky
From Proteopedia
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SOLUTION STRUCTURE OF PI7, A NON TOXIC PEPTIDE ISOLATED FROM THE SCORPION PANDINUS IMPERATOR.
Overview
The three-dimensional solution structure of a novel peptide, Pi7, purified, from the venom of the scorpion Pandinus imperator, and for which no, specific receptor has been found yet, was determined by two-dimensional, homonuclear proton NMR methods from a nanomole amount of compound using a, nano-nmr probe. Pandinus imperator peptide 7 does not block, voltage-dependent K(+)-channels and does not displace labeled noxiustoxin, from rat brain synaptosomal membranes. The toxin has 38 amino acid, residues and, similarly to Pi1, is stabilized by four disulfide bridges, (Cys6-Cys27, Cys12-Cys32, Cys16-Cys34, and Cys22-Cys37). In addition, the, lysine at position 26 crucial for potassium-channel blocking is replaced, in Pi7 by an arginine. Tyrosine 34, equivalent to Tyr36 of ChTX is, present, but the N-terminal positions 1 and 2 are occupied by two acidic, residues Asp and Glu, respectively. The dihedral angles and distance, restraints obtained from measured NMR parameters were used in structural, calculations in order to determine the conformation of the peptide. The, disulfide-bridge topology was established using distance restraints, allowing ambiguous partners between S atoms combined with NMR-derived, structural information. The structure is organized around a short, alpha-helix spanning residues Thr9 to Thr20/Gly21 and a beta-sheet. These, two elements of secondary structure are stabilized by two disulfide, bridges, Cys12-Cys32 and Cys16-Cys34. The antiparallel beta-sheet is, composed of two strands extending from Asn22 to Cys34 with a tight turn at, Ile28-Asn29 in contact with the N-terminal fragment Ile4 to Cys6.
About this Structure
1QKY is a Single protein structure of sequence from Pandinus imperator. Full crystallographic information is available from OCA.
Reference
Pi7, an orphan peptide from the scorpion Pandinus imperator: a 1H-NMR analysis using a nano-NMR Probe., Delepierre M, Prochnicka-Chalufour A, Boisbouvier J, Possani LD, Biochemistry. 1999 Dec 21;38(51):16756-65. PMID:10606507
Page seeded by OCA on Wed Nov 21 00:47:02 2007
