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Thermodynamic analysis of three state denaturation of Peanut Agglutinin
Author(s) -
Dev Sagarika,
Nirmala Devi K.,
Sinha Sharmistha,
Surolia Avadhesha
Publication year - 2006
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 - 10.1080/15216540600902228
Subject(s) - molten globule , denaturation (fissile materials) , chemistry , tetramer , crystallography , urea , oligomer , fluorescence , guanidine , circular dichroism , organic chemistry , nuclear chemistry , quantum mechanics , enzyme , physics
Peanut Agglutinin (PNA) is a homotetrameric protein with a very unusual open quaternary structure. During denaturation, it first dissociates into a molten globule like state, which subsequently undergoes complete denaturation. Urea denaturation of PNA at neutral pH has been studied by intrinsic fluorescence spectroscopy and has been fitted to a three state model, A4 ⇔ 4I ⇔ 4U, to get all the relevant thermodynamic parameters. Urea denaturation leads to continuous red shift of wavelength maxima. The molten globule like state is formed in a short range of urea concentration. Refolding of the denatured PNA has been attempted by intrinsic fluorescence study. Refolding by instantaneous dilution shows the occurrence of the formation of an intermediate at a relatively rapid rate, within few seconds. The transition from PNA tetramer to molten globule like state is found to have a ΔG value of ∼33 kcal/mole while it is ∼8 kcal/mole for the transition from molten globule like state to a completely denatured state. This in turn indicates that the tetramerization in PNA contributes significantly to the stability of the oligomer.iubmb Life, 58: 549‐555, 2006