期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
卷 1798, 期 6, 页码 1244-1249出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2010.03.010
关键词
Codon usage; Protein folding; Protein export; Maltose binding protein
资金
- University of Queensland
- CJ Martin Biomedical Fellowship (NHMRC) [569913]
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 degrees C instead of 37 degrees C, suggesting that the signal sequence optimised MBP protein (MBP-opt) may be misfolded, and is being degraded at 37 degrees C. Consistent with this idea, transient induction of the heat shock proteases prior to MBP expression at 28 degrees 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 degrees 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. (C) 2010 Elsevier B.V. All rights reserved.
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