Differences in the Structural Stability and Cooperativity between Monomeric Variants of Natural and de Novo Cro Proteins Revealed by High-Pressure Fourier Transform Infrared Spectroscopy

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• 作者：Hiroshi Imamura ; Yasuhiro Isogai ; Minoru Kato
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：May 1, 2012
• 年：2012
• 卷：51
• 期：17
• 页码：3539-3546
• 全文大小：466K
• 年卷期：v.51,no.17(May 1, 2012)
• ISSN：1520-4995

文摘

It is widely accepted that pressure affects the structure and dynamics of proteins; however, the underlying mechanism remains unresolved. Our previous studies have investigated the effects of pressure on fundamental secondary structural elements using model peptides, because these peptides represent a basis for understanding the effects of pressure on more complex structures. This study targeted monomeric variants of naturally occurring bacteriophage 位 Cro (natural Cro) and de novo designed 位 Cro (SN4m), which are 伪 + 尾 proteins. The sequence of SN4m is 75% different from that of natural Cro, but the structures are almost identical. Consequently, a comparison of the folding properties of these proteins is of interest. Pressure- and temperature-variable Fourier transform infrared spectroscopic analyses revealed that the 伪-helices and 尾-sheets of natural Cro are cooperatively and reversibly unfolded by pressure and temperature, whereas those of SN4m are not cooperatively unfolded by pressure; i.e., the 伪-helices of SN4m unfold at significantly higher pressures than the 尾-sheets and irreversibly unfold with increases in temperature. The higher unfolding pressure for the 伪-helices of SN4m indicates the presence of an intermediate structure of SN4m that does not retain 尾-sheet structure but does preserve the 伪-helices. These results demonstrate that the 伪-helices of natural Cro are stabilized by global tertiary contacts among the 伪-helices and the 尾-sheets, whereas the 伪-helices of SN4m are stabilized by local tertiary contacts between the 伪-helices.