Protein folding by a quasi-static-like process: a first-order state transition.
In this paper we report that quasi-static-like processes, in which stable intermediates were introduced carefully and deliberately, may be used to reversibly unfold and refold purified native porcine growth hormone. Through circular dichroism (CD) and dynamic light scattering (DLS), we were able to study the secondary structure conformational changes, tertiary structure thermal stabilities, and the particle size distributions of both the intermediates and the final folded product. The CD data showed that the secondary structure was restored in the initial folding stage, whereas the tertiary structure within the protein was restored one step before the last folding stage, as elucidated by thermal stability experiments. DLS analysis suggested that the average hydrodynamic radii of the folding intermediates shrunk to nativelike size immediately after the first folding stage. Our data suggested that the denaturant-containing protein folding reaction is a first-order-like state transition process. This quasi-static-like process may be useful in the prevention of aggregate formation in protein purification and thus can be used in protein engineering to improve the overall yield from harvesting proteins.
Chang
Chia-Ching
CC
Department of Physics, National Dong Hwa University, Hualien, Taiwan 97401. chiaching@mail.ndhu.edu.tw
Su
Ya-Chi
YC
Cheng
Ming-Sung
MS
Kan
Lou-Sing
LS
D000818:Animals; D002942:Circular Dichroism; D013006:Growth Hormone / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008027:Light; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D013552:Swine; D013696:Temperature
D013006:Growth Hormone