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Native like structure and stability of apo AI in a n ‐propanol/water solution as determined by 13 C NMR
Author(s) -
Leroy Arnaud,
Lippens Guy,
Wieruszeski Jean-Michel,
Parra Henri-Joseph,
Fruchart Jean-Charles
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00134-u
Subject(s) - circular dichroism , chemistry , denaturation (fissile materials) , protein secondary structure , native state , crystallography , stereochemistry , biochemistry , nuclear chemistry
To elucidate the molecular details of the conformation of apolipoprotein AI (apo AI), we have developed an approach related to the solubilization of this protein in 30% n ‐propanol. We have previously reported the promotion of a native‐like structure for apo AI solubilized in n ‐propanol, as depicted by circular dichroism, fluorescence, and limited proteolytic digestion as compared to the lipid associated form of apo AI. In the present study, we labeled the Lys residues of apo AI with 13 C by reductive methylation and used 13 C NMR to confirm the formation of a native‐like structure of apo AI in this environment. Furthermore, by the above criteria (circular dichroism and 13 C NMR) and by using urea and temperature as denaturing agents, we show that the denaturation of the native‐like structure of apo AI in n ‐propanol is a biphasic process. These studies show that in 30% n ‐propanol, apo AI contains two independently folded structural domains, of markedly different stabilities that might correspond to the amino‐terminal and the carboxy‐terminal halves of the molecule.