Structural basis for allosteric stimulation of Sir2 activity by Sir4 binding

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Sir2 (silent information regulator 2) is a key NAD-dependent deacetylase in yeast.
• Its function in transcriptional silencing involves both catalytic and regulatory domains.
• The N-terminal regulatory domain (Sir2N) function is poorly understood.

Purpose of the Study:

• To elucidate the structure and function of the Sir2 N-terminal regulatory domain.
• To understand how Sir4 interacts with Sir2 to regulate its activity.

Main Methods:

• X-ray crystallography was used to determine the structure of Sir2 in complex with a Sir4 fragment.
• Biochemical assays were performed to assess the role of the Sir4-Sir2 interaction in deacetylase activity.

Main Results:

• The crystal structure revealed Sir4 binding to Sir2N and the interdomain interface.
• A long loop of Sir4 was observed to contact the interface between Sir2N and the catalytic domains.
• This interaction was found to be critical for the allosteric stimulation of Sir2 deacetylase activity.

Conclusions:

• The study reveals the structure of the Sir2 regulatory domain and its interaction with Sir4.
• This interaction is crucial for the allosteric regulation of Sir2's deacetylase activity.
• Findings provide insights into the general mechanism of sirtuin allosteric regulation.