A Partially Unfolded Structure of the Alkaline-Denatured State of Pepsin and Its Implication for Stability of the Zymogen-Derived Protein
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- 作者：Takashi Konno ; Yuji O. Kamatari ; Naoki Tanaka ; Hironari Kamikubo ; Christopher M. Dobson ; and Kuniaki Nagayama
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：April 11, 2000
- 年：2000
- 卷：39
- 期：14
- 页码：4182 - 4190
- 全文大小：101K
- 年卷期：v.39,no.14(April 11, 2000)
- ISSN：1520-4995
文摘
Pepsin, a gastric aspartic proteinase, is a zymogen-derived protein that undergoes irreversiblealkaline denaturation at pH 6-7. Detailed knowledge of the structure of the alkaline-denatured state is animportant step in understanding the mechanism of the formation of the active enzyme. An extensiveanalysis of the denatured state at pH 8.0 was performed using a variety of techniques including 1H nuclearmagnetic resonance spectroscopy and solution X-ray scattering. This analysis indicates that the denaturedstate under these conditions has a compact and globular conformation with a substantial amount of secondaryand tertiary structures. The data suggest that this partially structured species has a highly folded regionand a flexible region. The NMR measurements suggest that the folded region contains His53 and is locatedat least partly in the N-terminal lobe of the protein. The alkaline-denatured state experiences a furtherreversible denaturation step at higher pH or on heating; the midpoints of the unfolding transition are pH11.5 (at 25 
C) and 53.1 C (at pH 8.0), respectively. The present findings suggest that the proteolyticprocessing of pepsinogen has substantially modified the ability of the protein to fold, such that its foldingprocess cannot progress beyond the partially folded intermediate of pepsin.
C) and 53.1 C (at pH 8.0), respectively. The present findings suggest that the proteolyticprocessing of pepsinogen has substantially modified the ability of the protein to fold, such that its foldingprocess cannot progress beyond the partially folded intermediate of pepsin.