The effect of pH on the unfolding pathway and stability of ribosome-inactivating protein abrin-II.
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.
Krupakar
J
J
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, India.
Das
P K
PK
Podder
S K
SK
D000036:Abrin / Q000737:chemistry*; D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D002942:Circular Dichroism; D019791:Guanidine; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D017510:Protein Folding; D013050:Spectrometry, Fluorescence
D000817:Anilino Naphthalenesulfonates; D000036:Abrin; C027132:1-anilino-8-naphthalenesulfonate; D019791:Guanidine