2D-04 Transcription regulation by FFRPs in Archaeal and Eubacterial cells 5： Mechanisms of discriminating between ligands by FFRPs

An FFRP from Pyrococcus OT3, DM1, was crystallized in complex with isoleucine, the ligand facilitating formation of octamers, i. e. tetrameric assemblies of dimers, and then with methionine another ligand facilitating diassembling of such octamers. By determining and comparing the two structures, residues of FFRPs in general binding to the two termini of amino acids, those discriminating between side-chains of amino acids, and those differentiating the effects, i. e. facilitating or repressing assembling, were identified. By analyzing the amino acid sequences of other FFRPs from P. OT3, assembling of FL11 in the presence of lysine and that of FL4 in the presence of glutamic acid were predicted and experimentally confirmed.