Acta Chimica Sinica ›› 2020, Vol. 78 ›› Issue (9): 994-1000.

Article

### 无序随机多肽组分相关的结构转变的蒙特卡洛模拟:以赖氨酸、谷氨酸和异亮氨酸组成的随机多肽为例

1. a 湖北医药学院 公共卫生与管理学院 十堰 442000;
b 湖北省南水北调水源区生物医药研发检测共享平台 十堰 442000;
c 东京大学 综合文化研究科广域科学专攻相关基础科学系 日本东京 153-8902
• 投稿日期:2020-06-18 发布日期:2020-07-15
• 通讯作者: 唐乾元, 鲍磊, 康文斌 E-mail:tangqianyuan@gmail.com;bolly@whu.edu.cn;wbkang@hbmu.edu.cn
• 基金资助:
项目受国家自然科学基金（No.11947006）、湖北医药学院人才启动金项目（Nos.2019QDJZR12，2018QDJZR22）和湖北省教育厅科学技术研究项目（No.B2018434）资助.

### Monte Carlo Simulations of Composition-Related Structural Transition of Disordered Peptides: The Case Study of Random Peptides Composed of Lysine, Glutamic Acids and Isoleucine

Zhang Pengchenga, Guo Jiaa, Zhu Gena, Fang Wenyua, Tang Qianyuanc, Bao Leia,b, Kang Wenbina,b

1. a Public Health and Management School, Hubei University of Medicine, Shiyan 442000, China;
b Hubei Biomedical Detection Sharing Platform in Water Source Area of South to North Water Diversion Project, Shiyan 442000, China;
c Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
• Received:2020-06-18 Published:2020-07-15
• Supported by:
Project supported by the National Natural Science Foundation of China (No. 11947006), the Cultivating Project for Young Scholar at Hubei University of Medicine (Nos. 2019QDJZR12, 2018QDJZR22), and the Natural Science Foundation of Hubei Provincial Department of Education (No. B2018434).

Intrinsically disordered proteins (IDPs) are a unique class of proteins without stable native structures. Like globular proteins, the structure and the dynamics of IDPs are also encoded in their amino acid sequences. IDPs usually contain a larger proportion of hydrophilic or charged amino acids than globular proteins. Interestingly, even with the same hydrophobicity and number of charged residues, the differences in sequence arrangement can lead to different structures of the peptides. In this work, to model such an effect, we conduct molecular simulations based on a series of peptides with randomly composed of charged residues (including glutamic acids and lysines) and isoleucine. In the simulation, we use the ABSINTH (self-Assembly of Biomolecules Studied by an Implicit, Novel, and Tunable Hamiltonian) implicit solvation model and employ the all-atom Markov Chain Monte Carlo method with replica-exchange sampling. Our simulations clearly show a transition between the extended conformations to compact structures for each peptide. The corresponding transition temperature is found to be dependent on the portion of the hydrophobic and charged residues. When the mean hydrophobicity is larger than a certain threshold, the transition temperature is higher than the room temperature, and vice versa. Such a result has outlined the borderline between intrinsically disordered proteins and the folded proteins. It is also consistent with previous analysis based on bioinformatics techniques. Furthermore, the contributions of different kinds of interactions to the structural variation of peptides are analyzed based on the contact statistics and the charge-pattern dependence of the gyration radii of the peptides. Our simulation results imply that the hydrophobicity of the sequence dominates the order-disorder transitions of IDPs, while the charge distribution can also affect such transitions. Based on these results, we achieve a comprehensive understanding of the sequence-structure relation of the natural proteins and the underlying physics. Our results may broaden our perspective of the sequence-structure relation of protein systems and shed light on the design of both ordered and disordered proteins.