In:
Biochemical Journal, Portland Press Ltd., Vol. 377, No. 2 ( 2004-01-15), p. 385-394
Abstract:
Both imperatoxin A (IpTxa), a 33-residue peptide toxin from scorpion venom, and peptide A, derived from the II–III loop of dihydropyridine receptor (DHPR), interact specifically with the skeletal ryanodine receptor (RyR1), which is a Ca2+-release channel in the sarcoplasmic reticulum, but with considerably different affinities. IpTxa activates RyR1 with nanomolar affinity, whereas peptide A activates RyR1 at micromolar concentrations. To investigate the molecular basis for high-affinity activation of RyR1 by IpTxa, we have determined the NMR solution structure of IpTxa, and identified its functional surface by using alanine-scanning analogues. A detailed comparison of the functional surface profiles for two peptide activators revealed that IpTxa exhibits a large functional surface area (approx. 1900 Å2, where 1 Å=0.1 nm), based on a short double-stranded antiparallel β-sheet structure, while peptide A bears a much smaller functional surface area (approx. 800 Å2), with the five consecutive basic residues (Arg681, Lys682, Arg683, Arg684 and Lys685) being clustered at the C-terminal end of the α-helix. The functional surface of IpTxa is composed of six essential residues (Leu7, Lys22, Arg23, Arg24, Arg31 and Arg33) and several other important residues (His6, Lys8, Arg9, Lys11, Lys19, Lys20, Gly25, Thr26, Asn27 and Lys30), indicating that amino acid residues involved in RyR1 activation make up over the half of the toxin molecule with the exception of cysteine residues. Taken together, these results suggest that the site where peptide A binds to RyR1 belongs to a subset of macrosites capable of being occupied by IpTxa, resulting in differing the affinity and the mode of activation.
Type of Medium:
Online Resource
ISSN:
0264-6021
,
1470-8728
Language:
English
Publisher:
Portland Press Ltd.
Publication Date:
2004
detail.hit.zdb_id:
1473095-9
SSG:
12
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