A SIR-tain Acetyl Complex Is Caught by a Sulfur Trap

In this issue, Hawse et al. (2008) provide additional insight into the mechanistic properties of sirtuin enzymes by describing the structure of a thio-imidate in the active site of Thermatoga maritima Sir2, which strengthens the proposal that the enzyme directly couples NAD+ and acetyllysine oxygen to form a versatile ADPR-peptidyl-imidate intermediate.