The included sequences are Sirt1-197-542 (full length, 747 amino acids (a.a.)), Sirt2-54-370 (389 a.a.), Sirt3-107-391 (399 a.a.), Sirt4-31-312 (314 a.a.), Sirt5-20-305 (310 a.a.), Sirt6-20-305 (355 a.a.), and Sirt7-71-347 (400 a.a.). The residues of Sirt3 that interact with crotonyl lysine in the crystal structure of the Sirt3–H3K4Cr complex are indicated (▼) above the residues and labeled with the Sirt3 sequence number. Highlighted in green is the Phe180 of Sirt3, which is involved in recognition of the crotonyl lysine via a π−π stacking interaction, and is conserved in Sirt1 and Sirt2, but not in the other sirtuins. The alignment was done by T-coffee (Notredame C, Higgins DG, and Heringa, J. 2000, Journal of Molecular Biology 302, 205–17).