A gating mechanism for Pi release governs the mRNA unwinding by eIF4AI during translation initiation.

Junyan Lu, Chenxiao Jiang, Xiaojing Li, Lizhi Jiang, Zengxia Li, Tilman Schneider-Poetsch, Jianwei Liu, Kunqian Yu, Jun O Liu, Hualiang Jiang, Cheng Luo, Yongjun Dang

Journal: Nucleic acids research 2016;43(21):10157-67

PMID: 26464436

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Abstract

Eukaryotic translation initiation factor eIF4AI, the founding member of DEAD-box helicases, undergoes ATP hydrolysis-coupled conformational changes to unwind mRNA secondary structures during translation initiation. However, the mechanism of its coupled enzymatic activities remains unclear. Here we report that a gating mechanism for Pi release controlled by the inter-domain linker of eIF4AI regulates the coupling between ATP hydrolysis and RNA unwinding. Molecular dynamic simulations and experimental results revealed that, through forming a hydrophobic core with the conserved SAT motif of the N-terminal domain and I357 from the C-terminal domain, the linker gated the release of Pi from the hydrolysis site, which avoided futile hydrolysis cycles of eIF4AI. Further mutagenesis studies suggested this linker also plays an auto-inhibitory role in the enzymatic activity of eIF4AI, which may be essential for its function during translation initiation. Overall, our results reveal a novel regulatory mechanism that controls eIF4AI-mediated mRNA unwinding and can guide further mechanistic studies on other DEAD-box helicases.

Address: Key Laboratory of Metabolism and Molecular Medicine, the Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.; Key Laboratory of Metabolism and Molecular Medicine, the Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.; Chemical Genetics Laboratory, RIKEN, Wako, Saitama, 351-0198, Japan.; Department of Chemistry, Shanghai Key Lab of Chemical Biology for Protein Research & Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, China.; Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.; Department of Pharmacology & Molecular Sciences and Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.; Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China [email protected].; Key Laboratory of Metabolism and Molecular Medicine, the Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China [email protected].

DOI: 10.1093/nar/gkv1033