PDBsum entry 6z3a

Hydrolase

PDB id: 6z3a

Contents

Protein chains

2311 a.a.

554 a.a.

Ligands

ANP ×2

Metals

_ZN ×2

References listed in PDB file

Key reference

• Title: Mechanism of auto-Inhibition and activation of mec1^atr checkpoint kinase.
• Authors: E.A.Tannous, L.A.Yates, X.Zhang, P.M.Burgers.
• Ref.: Nat Struct Mol Biol, 2021, 28, 50-61. [DOI no: 10.1016/j.jsb.2012.09.006]
• PubMed id: 33169019

Abstract

In response to DNA damage or replication fork stalling, the basal activity of Mec1^ATR is stimulated in a cell-cycle-dependent manner, leading to cell-cycle arrest and the promotion of DNA repair. Mec1^ATR dysfunction leads to cell death in yeast and causes chromosome instability and embryonic lethality in mammals. Thus, ATR is a major target for cancer therapies in homologous recombination-deficient cancers. Here we identify a single mutation in Mec1, conserved in ATR, that results in constitutive activity. Using cryo-electron microscopy, we determine the structures of this constitutively active form (Mec1(F2244L)-Ddc2) at 2.8 Å and the wild type at 3.8 Å, both in complex with Mg²⁺-AMP-PNP. These structures yield a near-complete atomic model for Mec1-Ddc2 and uncover the molecular basis for low basal activity and the conformational changes required for activation. Combined with biochemical and genetic data, we discover key regulatory regions and propose a Mec1 activation mechanism.