The chimeric peptide [Lys(-2)-Arg(-1)]-sarafotoxin-S6b, composed of the endothelin pro-sequence and sarafotoxin, retains the salt-bridge staple between Arg(-1) and Asp8 previously observed in [Lys(-2)-Arg(-1)]-endothelin. Implications of this salt-bridge in the contractile activity and the oxidative folding reaction.
The chimeric peptide [Lys(-2)-Arg(-1)]-sarafotoxin-S6b (KR-SRTb) designed from the Lys-2-Arg-1 dipeptide of the endothelin pro-sequence and the sarafotoxin-S6b sequence was synthesized. Its contractile activity was found to be decreased markedly when compared with that of the parent SRTb. In contrast, the extension by the Lys-Arg dipeptide was found to increase the formation of the native disulfide isomer (82/18 versus 96/4) when the reaction was carried out in the presence of redox reagents. The solution structure of KR-SRTb was determined by NMR as a function of pH. In the carboxylic acid state, the structure consists of the cystine-stabilized alpha-helical motif, with the alpha-helical part spanning residues 9-15, and of an unstructured C-terminal tail. In the carboxylate state, the structure is characterized by a salt-bridge between Arg(-1) and Asp8, which we identified previously in the [Lys(-2)-Arg(-1)]-endothelin-1 peptide (KR-ET-1). The fact that this salt-bridge is commonly observed in KR-SRTb and KR-ET-1, despite the 33% sequence difference between the corresponding parental peptides, highlights the remarkable adaptability of the Lys-Arg extension for the formation of a special salt-bridge. As a consequence, this salt-bridge, which does not depend on either the 4-7 sequence of the loop or the C-terminal sequence, appears to be particularly well suited to improve the stability of the cystine-stabilized alpha-helical motif. Therefore, because of its high yield in the native disulfide arrangement and its high permissiveness for sequence mutation in the 4-7 loop, such a stabilized cystine-stabilized alpha-helical motif could be a valuable scaffold for the presentation of a library of constrained short peptides.
Aumelas
A
A
Centre de Biochimie Structurale, CNRS UMR C9955, INSERM U414, Faculté de Pharmacie, Montpellier, France. aumelas@cbs.univ-montp1.fr
Chiche
L
L
Kubo
S
S
Chino
N
N
Watanabe
T X
TX
Kobayashi
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D004220:Disulfides / Q000737:chemistry; D019332:Endothelin-1 / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D012492:Salts; D013329:Structure-Activity Relationship; D014662:Vasoconstrictor Agents / Q000737:chemistry / Q000494:pharmacology; D014757:Viper Venoms / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*
D004220:Disulfides; D019332:Endothelin-1; D011993:Recombinant Fusion Proteins; D012492:Salts; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6