SNAP output for PDB entry 7ai5 [SNAP web server]

PDB-id

7ai5; SNAP-derived features in text and JSON formats; DNAproDB

Class

DNA binding protein

Method

cryo-EM (4.4 Å)

Summary

Muts in scanning state

Reference

Fernandez-Leiro R, Bhairosing-Kok D, Kunetsky V, Laffeber C, Winterwerp HH, Groothuizen F, Fish A, Lebbink JHG, Friedhoff P, Sixma TK, Lamers MH (2021): "The selection process of licensing a DNA mismatch for repair." Nat.Struct.Mol.Biol., 28, 373-381. doi: 10.1038/s41594-021-00577-7.

Abstract

DNA mismatch repair detects and removes mismatches from DNA by a conserved mechanism, reducing the error rate of DNA replication by 100- to 1,000-fold. In this process, MutS homologs scan DNA, recognize mismatches and initiate repair. How the MutS homologs selectively license repair of a mismatch among millions of matched base pairs is not understood. Here we present four cryo-EM structures of Escherichia coli MutS that provide snapshots, from scanning homoduplex DNA to mismatch binding and MutL activation via an intermediate state. During scanning, the homoduplex DNA forms a steric block that prevents MutS from transitioning into the MutL-bound clamp state, which can only be overcome through kinking of the DNA at a mismatch. Structural asymmetry in all four structures indicates a division of labor between the two MutS monomers. Together, these structures reveal how a small conformational change from the homoduplex- to heteroduplex-bound MutS acts as a licensing step that triggers a dramatic conformational change that enables MutL binding and initiation of the repair cascade.