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The effect of pH on the unfolding pathway and stability of ribosome‐inactivating protein abrin‐II
Author(s) -
Krupakar Jayarapu,
Das Puspendu K.,
Podder Sunil K.
Publication year - 1998
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549800203932
Subject(s) - chemistry , protein stability , ribosome , biophysics , biochemistry , biology , rna , gene
Abstract The effect of pH on the unfolding pathway and the stability of the toxic protein abrin‐II have been studied by increasing denaturant concentrations of guanidine hydrochloride and by monitoring the change in 8,1‐anilino naphthalene sulfonic acid (ANS) fluorescence upon binding to the hydrophobic sites of the protein. Intrinsic protein fluorescence, far and near UV‐circular dichroism (CD) spectroscopy and ANS binding studies reveal that the unfolding of abrin‐II occurs through two intermediates at pH 7.2 and one intermediate at pH 4.5. At pH 7.2, the two subunits A and B of abrin‐II unfold sequentially. The native protein is more stable at pH 4.5 than at pH 7.2. However, the stability of the abrin‐II A‐subunit is not affected by a change in pH. These observations may assist in an understanding of the physiologically relevant transmembrane translocation of the toxin.