Amino acid sequence of α-IPMS containing two copies of the VNTR. The N-terminal domain (catalytic domain), residues 51–368, is colored red. Residues involved in substrate (α-KIV) binding are underlined: D81, H285, H287, N321, E309 and G320. The conserved GxGERxG motif (residues 314–320, H379 and Y410), which forms a groove possible for acetyl CoA binding, is underlined. Linker domain: subdomain I (residues 369–424) is colored blue; subdomain II (residues 434–490) is colored magenta. The C-terminal regulatory domain (residues 491–644) is colored green. The two copies (one copy contains 19 amino acids, vtiaspaqpgeagrhasdp, at residues 575–612) of the repeat sequence are underlined. The hydrophilic and charged residues are in bold. Residues involved in leucine binding are indicated in bold italics: L535, A536, V551, Y554, A565 and A567. Mutation of residues G531, G533 and A536 (underlined) abolished feedback inhibition of α-IPMS in S. cerevisiae. The Y410F mutant form of M. tuberculosis α-IPMS was insensitive to feedback inhibition.