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Noncooperative temperature melting of a globular protein without specific tertiary structure: Acid form of bovine carbonic anhydrase B
Author(s) -
Brazhnikov E. V.,
Chirgadze Yu. N.,
Dolgikh D. A.,
Ptitsyn O. B.
Publication year - 1985
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360241005
Subject(s) - chemistry , molten globule , globular protein , carbonic anhydrase , protein tertiary structure , crystallography , antiparallel (mathematics) , globular cluster , carbonic anhydrase ii , native state , molecule , protein secondary structure , denaturation (fissile materials) , melting point , circular dichroism , biochemistry , enzyme , organic chemistry , nuclear chemistry , physics , quantum mechanics , galaxy , magnetic field
Heat denaturation of native globular proteins is a cooperative process usually connected with the melting of the main part of their regular secondary structure. In this paper, a noncooperative temperature‐induced melting of the regular secondary structure in the carbonic anhydrase B at pH 2.6 in heavy water is observed by ir spectroscopy. The molecules of carbonic anhydrase B in an acid medium, unlike the native ones, do not have a specific tertiary structure. Nevertheless, the β‐structure content is about the same in both of these states. A temperature‐induced noncooperative melting process takes place from 10 to 67°C with a decrease of the antiparallel β‐form content by about one third. The remaining part of the β‐form melts with a more intensive heat absorption, with a maximum at 87°C. The whole melting process is practically reversible. We assume that the observed noncooperative process displays a general property of a new type of structural state of the globular protein—the “molten globule state.”