The structure of the putative Se-Met streptothricin acetyltransferase from Bacillus anthracis str. Ames in complex with acetyl coenzyme A was solved by SAD. The protein is mostly β-stranded (40 %) with 20 % of the helical component. The core of the enzyme is a six-stranded antiparallel β-sheet, which ideal alignment is disrupted by the aliphatic tail of Acetyl-CoA. The tail mimics β-strand-β-strand hydrogen bonding interactions, making the sheet quasi seven-stranded. Each of three copies of the protein binds a single Acetyl-CoA molecule, which electron density is well defined. The chains B and C form a dimer with the buried surface area of 2140 A2, whereas chain A makes identical dimer with a symmetry related molecule with 2480 A2 of buried surface area. Monomers in the dimer interact such a way that a six-stranded antiparallel β-sheet is formed.