9MX5

Cryo-EM structure of ancestral Dicer helicase bound to 27-bp dsRNA in internally-bound transition state

9MX5 の概要

• エントリーDOI: 10.2210/pdb9mx5/pdb
• 関連するPDBエントリー: 9MW7
• EMDBエントリー: 48710
• 分子名称: AncD1D2, RNA (27-MER), ALUMINUM FLUORIDE, ... (6 entities in total)
• 機能のキーワード: rna helicase, dsrbm, antiviral protein-rna complex, antiviral protein/rna
• 由来する生物種: synthetic construct; 詳細
• タンパク質・核酸の鎖数: 3
• 化学式量合計: 93246.39

構造登録者

Aderounmu, A.M.,Consalvo, C.D.,Shen, P.S.,Bass, B.L. (登録日: 2025-01-17, 公開日: 2025-03-12, 最終更新日: 2025-06-04)

主引用文献

Aderounmu, A.M.,Maus-Conn, J.,Consalvo, C.D.,Shen, P.S.,Bass, B.L.
Biochemical and structural basis of Dicer helicase function unveiled by resurrecting ancient proteins.
Proc.Natl.Acad.Sci.USA, 122:e2500825122-e2500825122, 2025

PubMed Abstract: A fully functional Dicer helicase, present in the modern arthropod, uses energy from ATP hydrolysis to power translocation on bound dsRNA, enabling the processive dsRNA cleavage required for efficient antiviral defense. However, modern Dicer orthologs exhibit divergent helicase functions that affect their ability to contribute to antiviral defense. Moreover, mechanisms that couple ATP hydrolysis to Dicer helicase movement on dsRNA remain enigmatic. We used biochemical and structural analyses of ancestrally reconstructed Dicer helicases to map evolution of dsRNA binding affinity, ATP hydrolysis and translocation. Loss of affinity for dsRNA occurred early in Dicer evolution, coinciding with a decline in translocation activity, despite preservation of ATP hydrolysis activity. Ancestral nematode Dicer also exhibited significant decline in ATP hydrolysis and translocation, but studies of antiviral activities in the modern nematode indicate Dicer retained a role in antiviral defense by recruiting a second helicase. Cryogenic electron microscopy (cryo-EM) analyses of an ancient metazoan Dicer allowed capture of multiple helicase states revealing the mechanism that connects each step of ATP hydrolysis to unidirectional movement along dsRNA. Our study rationalizes the diversity in modern Dicer helicases by connecting ancestral functions to observations in extant enzymes.

PubMed: 40434637
DOI: 10.1073/pnas.2500825122

実験手法

ELECTRON MICROSCOPY (3.1 Å)