ISSN:
1573-3904
Keywords:
α-Helix
;
Carboxamide substitution
;
Circular dichroism
;
Disulfide isomer
;
KR-ET-1
;
Prosequence
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract An amino-terminal extension of endothelin-1 by the Lys-Arg dipeptide in the prosequence (KR-ET-1) greatly increased the ratio of native-type to non-native-type disulfide isomer (96/4 versus 71/29) during the oxidative folding reaction. This improvement was completely abolished by substituting Asn for Asp at position 8 (D8N-KR-ET-1), whereas most of it was maintained with similar carboxamide analogues replaced at Glu10 or Asp18. Structure analyses by circular dichroism spectroscopy revealed that (i) in the carboxylate state, the α-helical content of the native-type isomer of KR-ET-1 is higher than that of the native-type isomer of ET-1, while such a variation is not observed in the corresponding non-native-type isomer of KR-ET-1; and (ii) the enhanced α-helicity resulting from the Lys-Arg extension is largely diminished in D8N-KR-ET-1. From these results and our previous findings that the helical structure in KR-ET-1 is stabilized by a particular salt bridge between the extended Arg-1 basic moiety and either the Asp8 or Glu10 acidic side chain in ET-1 [Aumelas, A. et al., Biochemistry, 34 (1995) 4546], we conclude that the formation of a specific salt bridge between the side chains of Arg-1 and Asp8 in KR-ET-1 is critical for the predominant generation of the native-type disulfide isomer, probably because it stabilizes the helical structure of parental ET-1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008835323518
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