Fig. 6: Schematic model of MsmIMPDH allosteric regulation illustrating the interplay of nucleotide interactions and their impact on the activity and conformation of MsmIMPDH.
From: Deciphering the allosteric regulation of mycobacterial inosine-5′-monophosphate dehydrogenase
The top tetramer is depicted in blue, its opposite tetramer in gold, and the CBS domains in shades of grey. a The CBS domains are free in the apo form that exists in both tetrameric and octameric conformations. c The binding of ATP to Site 1 stabilizes the dimers of the CBS domains and thus the octameric conformation. b, d IMP binding drives the formation of the active tetramers (b) or extended octamers stabilized by ATP (d). e, f This extension is blocked by the binding of GTP (e) or ppGpp (f), thus locking the hinge regions that link the CBS and catalytic domains (depicted as thick black linkers). g Binding of ATP to Site 2 competes with GTP and ppGpp, while enabling the IMP-induced extension.
