Related Experiment Video
Updated: Aug 11, 2026

Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes
Published on: April 4, 2025
Quaternary polymorphism of replicative helicase G40P: structural mapping and domain rearrangement
Rafael Núñez-Ramírez1, Yolanda Robledo, Pablo Mesa
1Department of Macro-molecular Structure, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain.
Abstract:
Quaternary polymorphism is a distinctive structural feature of the DnaB family of replicative DNA hexameric helicases. The Bacillus subtilis bacteriophage SPP1 gene 40 product (G40P) belongs to this family. Three different quaternary states have been described for G40P homohexamers, two of them with C(3) symmetry, and the other with C(6) symmetry. We present three-dimensional reconstructions of the different architectures of G40P hexamers and a variant lacking the N-terminal domain. Comparison of the G40P and the deletion mutant structures sheds new light on the functional roles of the N and C-terminal domains, at the same time that it allows the direct structural mapping of these domains. Based on this new information, hybrid EM/X-ray models are presented for all the different symmetries. These results suggest that quaternary polymorphism of hexameric helicases may be implicated in the translocation along the DNA.
Related Concept Videos
DNA Helicases
Restarting Stalled Replication Forks
The Replisome
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The Replisome
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
Homologous Recombination
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...

