Solution structure of Atg8 reveals conformational polymorphism of the N-terminal domain

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• Autophagy is a cellular process involving membrane formation to engulf and degrade cellular components.
• The Atg8 protein is essential for the initiation of autophagy, specifically the membrane expansion step.
• Atg8 undergoes a critical conjugation process with phosphatidylethanolamine.

Purpose of the Study:

• To determine the high-resolution structure of unprocessed Atg8 using nuclear magnetic resonance (NMR) spectroscopy.
• To investigate the dynamic behaviors of different Atg8 subdomains and compare cleaved versus uncleaved forms.
• To discuss the biological relevance of observed structural and dynamic differences.

Main Methods:

• High-resolution structure determination of unprocessed Atg8 via NMR spectroscopy.
• Analysis of protein dynamics using heteronuclear NOE data (pico- to nanosecond timescale).
• Characterization of conformational changes on the micro- to millisecond timescale.

Main Results:

• The C-terminal subdomain of unprocessed Atg8 exhibits a ubiquitin-like fold with slightly increased pico- to nanosecond mobility.
• Cleaved Atg8(G116) displays reduced mobility compared to the unprocessed form.
• The N-terminal domain of Atg8 exists in different conformations across the micro- to millisecond timescale.

Conclusions:

• Structural and dynamic analyses provide insights into Atg8's role in autophagy initiation.
• Differences in mobility between subdomains and between cleaved/uncleaved Atg8 may have significant biological implications.
• Understanding Atg8 dynamics is key to elucidating the molecular mechanisms of autophagosome formation.