Structural basis for the mechanism and regulation of Sir2 enzymes.
Molecular cell
confidence
Key findings
Structural study reveals NAD+ binding modes and proposes mechanism for Sir2 deacetylation and nicotinamide inhibition; no clinical/biological endpoints.
View source on PubMed (PMID 15023335) ↗
- Sample size
- N/A
- Population
- Not applicable (structural biology / enzymology study of Sir2Af2 archaeal protein)
- Dosing
- N/A
- Duration
- N/A
- Route
- N/A
- Blinding
- not_reported
- Controls
- not_reported
- Drug class
- coenzyme
Full abstract
Sir2 proteins form a family of NAD(+)-dependent protein deacetylases required for diverse biological processes, including transcriptional silencing, suppression of rDNA recombination, control of p53 activity, regulation of acetyl-CoA synthetase, and aging. Although structures of Sir2 enzymes in the presence and absence of peptide substrate or NAD(+) have been determined, the role of the enzyme in the mechanism of deacetylation and NAD(+) cleavage is still unclear. Here, we present additional structures of Sir2Af2 in several differently complexed states: in a productive complex with NAD(+), in a nonproductive NAD(+) complex with bound ADP-ribose, and in the unliganded state. We observe a new mode of NAD(+) binding that seems to depend on acetyl-lysine binding, in which the nicotinamide ring of NAD(+) is buried in the highly conserved "C" pocket of the enzyme. We propose a detailed structure-based mechanism for deacetylation and nicotinamide inhibition of Sir2 consistent with mutagenesis and enzymatic studies.