麦芽糖结合蛋白
蛋白酵素
信号肽
蛋白质折叠
生物化学
热休克蛋白
生物
信使核糖核酸
化学
肽序列
酶
基因
重组DNA
融合蛋白
作者
Yaramah M. Zalucki,Christopher E. Jones,Peggy Ng,Benjamin L. Schulz,Michael P. Jennings
标识
DOI:10.1016/j.bbamem.2010.03.010
摘要
Non-optimal codons are generally characterised by a low concentration of isoaccepting tRNA and a slower translation rate compared to optimal codons. In a previous study, we reported a 20-fold reduction in maltose binding protein (MBP) level when the non-optimal codons in the signal sequence were optimised. In this study, we report that the 20-fold reduction is rescued when MBP is expressed at 28 °C instead of 37 °C, suggesting that the signal sequence optimised MBP protein (MBP-opt) may be misfolded, and is being degraded at 37 °C. Consistent with this idea, transient induction of the heat shock proteases prior to MBP expression at 28 °C restores the 20-fold difference, demonstrating that the difference in production levels is due to post-translational degradation of MBP-opt by the heat-shock proteases. Analysis of the structure of purified MBP-wt and MBP-opt grown at 28 °C showed that although they have similar secondary structure content, MBP-opt is more resistant to thermal unfolding than is MBP-wt. The two proteins also exhibit different tryptic fragment profiles, further confirming that they are folded into conformationally different states. This is the first study to demonstrate that signal sequence non-optimal codons can influence the folding of the mature exported protein.
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