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Bypassing the kinetic trap of serpin protein folding by loop extension
Author(s) -
Im Hana,
Ahn HeeYoung,
Yu MyeongHee
Publication year - 2000
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.9.8.1497
Subject(s) - serpin , native state , chemistry , metastability , protein folding , folding (dsp implementation) , biophysics , beta sheet , protein structure , crystallography , chemical physics , stereochemistry , biochemistry , biology , electrical engineering , gene , engineering , organic chemistry
The native form of some proteins such as strained plasma serpins (serine protease inhibitors) and the spring‐loaded viral membrane fusion proteins are in a metastable state. The metastable native form is thought to be a folding intermediate in which conversion into the most stable state is blocked by a very high kinetic barrier. In an effort to understand how the spontaneous conversion of the metastable native form into the most stable state is prevented, we designed mutations of α1‐antitrypsin, a prototype serpin, which can bypass the folding barrier. Extending the reactive center loop of α1‐antitrypsin converts the molecule into a more stable state. Remarkably, a 30‐residue loop extension allows conversion into an extremely stable state, which is comparable to the relaxed cleaved form. Biochemical data strongly suggest that the strain release is due to the insertion of the reactive center loop into the major β‐sheet, A sheet, as in the known stable conformations of serpins. Our results clearly show that extending the reactive center loop is sufficient to bypass the folding barrier of α1‐antitrypsin and suggest that the constrain held by polypeptide connection prevents the conversion of the native form into the lowest energy state.