Structural insights into ubiquitin phosphorylation by PINK1

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• Mutations in PTEN-induced putative kinase 1 (PINK1) and parkin are linked to familial Parkinsonism.
• PINK1 and parkin are critical for degrading damaged mitochondria via ubiquitylation.
• PINK1 phosphorylates ubiquitin and parkin to regulate parkin activity.

Purpose of the Study:

• To elucidate the structural mechanism of ubiquitin/UBL phosphorylation by PINK1.
• To understand how PINK1 interacts with ubiquitin and parkin at a molecular level.

Main Methods:

• Determined the crystal structure of Tribolium castaneum PINK1 kinase domain (TcPINK1) complexed with an ATP analogue.
• Utilized crosslinking analyses to identify PINK1-ubiquitin interaction sites.
• Performed structure-guided mutational analyses.

Main Results:

• The crystal structure of TcPINK1 revealed its N- and C-terminal lobes and a PINK1-specific extension.
• A nonhydrolyzable ATP analogue was observed bound in the cleft between the lobes.
• A wider Ub/UBL-binding groove compared to other kinases was identified, suggesting specific accommodation for ubiquitin or UBL.
• Crosslinking identified a specific surface on ubiquitin interacting with PINK1.

Conclusions:

• The determined structure provides insights into the mechanism of PINK1-mediated phosphorylation of ubiquitin and parkin.
• The unique binding groove facilitates PINK1's role in mitochondrial quality control.
• Structure-guided mutations validated the proposed interaction model.