The AcmB has an α/β fold formed by three tightly packed domains. The molecule has an elongated shape with dimensions of 52 x 55 x 72 Å 3 , its volume equals 69445 Å 3 and a surface area of 21035 Å 2 . The overall architecture is very similar to KstD1 with a RMS deviation of 0.927 Å calculated for Cα. The largest, FAD-binding domain comprises helices H2-H5, H10-H13 and H21-H22 (Figure ). This domain also contains three β-sheets: the largest one, antiparallel β-sheet A (B1-B2, B10-B13 and B23), antiparallel β-sheet B (B3-B5) and small two-stranded β-sheet E (B14-B21). The second catalytic domain (A320-T498) consists of a six-stranded antiparallel β-sheet F (strands B15-B20) located in the core of the molecule decorated with seven helices (H14-H20). The third domain (Y153-R204) comprises a unique part, not observed in the KstD1 structure, which we believe serves as a region responsible for the association of the enzyme to the cell membrane.