Department of Biomedical Science, U1 University, Chungbuk 29131, Republic of Korea.
Department of Biochemistry and Cell Biology, Center for Advanced Biotechnology and Medicine (CABM), Rutgers-Robert Wood Johnson Medical School, 679 Hoes Lane, Piscataway, NJ 08854, USA.
J Biochem. 2020 May 1;167(5):473-482. doi: 10.1093/jb/mvaa004.
Nascent polypeptides are synthesized on ribosomes starting at the N-terminus and simultaneously begin to fold during translation. We constructed N-terminal fragments of prosubtilisin E containing an intramolecular chaperone (IMC) at N-terminus to mimic cotranslational folding intermediates of prosubtilisin. The IMC-fragments of prosubtilisin exhibited progressive enhancement of their secondary structures and thermostabilities with increasing polypeptide length. However, even the largest IMC-fragment with 72 residues truncated from the C-terminus behaved as a molten globule, indicating the requirement of the C-terminal region to have a stable tertiary structure. Furthermore, truncation of the IMC in the IMC-fragments resulted in aggregation, suggesting that the IMC plays a crucial role to prevent misfolding and aggregation of cotranslational folding intermediates during translation of prosubtilisin polypeptide.
新生多肽在核糖体上从 N 端开始合成，并在翻译过程中同时开始折叠。我们构建了含有 N 端分子伴侣 (IMC) 的 prosubtilisin E 的 N 端片段，以模拟 prosubtilisin 的共翻译折叠中间态。prosubtilisin 的 IMC 片段随着多肽长度的增加，其二级结构和热稳定性逐渐增强。然而，即使是从 C 端截断的 72 个残基的最大 IMC 片段，也表现为无规卷曲，这表明 C 端区域需要具有稳定的三级结构。此外，在 IMC 片段中截断 IMC 会导致聚集，表明 IMC 在 prosubtilisin 多肽翻译过程中防止共翻译折叠中间态的错误折叠和聚集中起着至关重要的作用。
