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The disulfide‐coupled folding pathway of apamin as derived from diselenide‐quenched analogs and intermediates
Author(s) -
Pegoraro Stefano,
Fiori Stella,
Cramer Jörg,
RudolphBöhner Sabine,
Moroder Luis
Publication year - 1999
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.8.8.1605
Subject(s) - apamin , selenocysteine , diselenide , chemistry , folding (dsp implementation) , protein folding , cysteine , stereochemistry , selenium , biochemistry , organic chemistry , enzyme , electrical engineering , calcium , engineering
The sequence of apamin, an 18 residue bee venom toxin, encloses all the information required for the correct disulfide‐coupled folding into the cystine‐stabilized α‐helical motif. Three apamin analogs, each containing a pair of selenocysteine residues replacing the related cysteines, were synthesized to mimic the three possible apamin isomers with two crossed, parallel, or consecutive disulfides, respectively. Refolding experiments clearly revealed that the redox potential of selenocysteine prevails over the sequence encoded structural information for proper folding of apamin. Thus, selenocysteine can be used as a new device to generate productive and nonproductive folding intermediates of peptides and proteins. In fact, disulfides are selectively reduced in presence of the diselenide and the conformational features derived from these intermediates as well as from the three‐dimensional (3D) structures of the selenocysteine‐containing analogs with their nonnatural networks of diselenide/disulfide bridges allowed to gain further insight into the subtle driving forces for the correct folding of apamin that mainly derive from local conformational preferences.