PMID: 28508083
Authors:
Baretic D, Pollard HK, Fisher DI, Johnson CM, Santhanam B, Truman CM, Kouba T, Fersht AR, Phillips C, Williams RL
Title:
Structures of closed and open conformations of dimeric human ATM.
Journal:
Sci Adv. 2017 May 10;3(5):e1700933. doi: 10.1126/sciadv.1700933. eCollection 2017, May.
Abstract:
ATM (ataxia-telangiectasia mutated) is a phosphatidylinositol 3-kinase-related protein kinase (PIKK) best known for its role in DNA damage response. ATM also functions in oxidative stress response, insulin signaling, and neurogenesis. Our electron cryomicroscopy (cryo-EM) suggests that human ATM is in a dynamic equilibrium between closed and open dimers. In the closed state, the PIKK regulatory domain blocks the peptide substrate-binding site, suggesting that this conformation may represent an inactive or basally active enzyme. The active site is held in this closed conformation by interaction with a long helical hairpin in the TRD3 (tetratricopeptide repeats domain 3) domain of the symmetry-related molecule. The open dimer has two protomers with only a limited contact interface, and it lacks the intermolecular interactions that block the peptide-binding site in the closed dimer. This suggests that the open conformation may be more active. The ATM structure shows the detailed topology of the regulator-interacting N-terminal helical solenoid. The ATM conformational dynamics shown by the structures represent an important step in understanding the enzyme regulation.