Existence of Different Structural Intermediates and Aggregates on the Folding Pathway of Ovalbumin |
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Authors: | Afshin Iram Aabgeena Naeem |
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Institution: | (1) Department of Biochemistry, Faculty of Life Science, Aligarh Muslim University, Aligarh, 202 002, India |
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Abstract: | Structural modifications of ovalbumin in presence of different concentration of guanidine hydrochloride (Gdn HCl) and glucose
were investigated by using intrinsic fluorescence, Fourier transform infra-red spectroscopy, circular dichroism and 8-anilino-1-naphthalene-sulphonic
acid, to confirm that partially folded intermediates of ovalbumin lead to aggregation. The two partially folded intermediates
of ovalbumin were observed one at 1 M Gdn HCl and another in the presence of 20 mM glucose at 3 M Gdn HCl. Both intermediates
exist as compact states with altered intrinsic fluorescence, prominent β-sheet secondary structure and enhanced ANS binding.
Ovalbumin in the presence of glucose required more concentration of Gdn HCl (3 M) to exist as an intermediate state than control
(1 M). Such alpha-helix/beta-sheet transition of proteins is a crucial step in amyloidogenic diseases and represents an internal
rearrangement of local contacts in an already folded protein. Further, incubation for 24 h resulted in the formation of aggregates
as detected by thioflavin T-assay. On further increasing the concentration of glucose to 50 mM and incubation time for various
days resulted in the formation of molten globule state of ovalbumin at 6th day. Later on, at 10th day advanced glycated end
products were observed. |
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