PDBsum entry 4tz6

RNA binding protein/RNA

PDB id: 4tz6

Contents

Protein chain

504 a.a.

DNA/RNA

Ligands

BEF

UDP

Metals

_MG

References listed in PDB file

Key reference

• Title: Molecular insights into RNA and DNA helicase evolution from the determinants of specificity for a dead-Box RNA helicase.
• Authors: A.L.Mallam, D.J.Sidote, A.M.Lambowitz.
• Ref.: Elife, 2014, 3, e04630. [DOI no: 10.7554/eLife.04630]
• PubMed id: 25497230

Abstract

How different helicase families with a conserved catalytic 'helicase core' evolved to function on varied RNA and DNA substrates by diverse mechanisms remains unclear. In this study, we used Mss116, a yeast DEAD-box protein that utilizes ATP to locally unwind dsRNA, to investigate helicase specificity and mechanism. Our results define the molecular basis for the substrate specificity of a DEAD-box protein. Additionally, they show that Mss116 has ambiguous substrate-binding properties and interacts with all four NTPs and both RNA and DNA. The efficiency of unwinding correlates with the stability of the 'closed-state' helicase core, a complex with nucleotide and nucleic acid that forms as duplexes are unwound. Crystal structures reveal that core stability is modulated by family-specific interactions that favor certain substrates. This suggests how present-day helicases diversified from an ancestral core with broad specificity by retaining core closure as a common catalytic mechanism while optimizing substrate-binding interactions for different cellular functions.