A type 1 glutamine amidotransferase (GATase1)-like domain found in PfpI from Pyrococcus furiosus
A type 1 glutamine amidotransferase (GATase1)-like domain found in PfpI from Pyrococcus furiosus. This group includes proteins similar to PfpI from P. furiosus. and PH1704 from Pyrococcus horikoshii. These enzymes are ATP-independent intracellular proteases and may hydrolyze small peptides to provide a nutritional source. Only Cys of the catalytic triad typical of GATase1 domains is conserved in this group. This Cys residue is found in the sharp turn between a beta strand and an alpha helix termed the nucleophile elbow. For PH1704, it is believed that this Cys together with a different His in one monomer and Glu (from an adjacent monomer) forms a different catalytic triad from the typical GATase1domain. PfpI is homooligomeric. Protease activity is only found for oligomeric forms of PH1704.