2.7.7.70 ? x * 19000, recombinant His6-tagged SeMet-labeled enzyme, SDS-PAGE -, 760292 2.7.7.70 ? x * 55000, SDS-PAGE 700026 2.7.7.70 dimer the wild-type overall architecture belongs to a three layer (alpha/beta/alpha) sandwich structure with a central beta-sheet topology followed by a C-terminal helix through a flexible loop. There are four protomers in the unit cell and all of them exist in a dimeric form. The different contacts of two dimeric pairs are presumed to be originated from different crystal packing environment. It implies inherent flexibility of the hinge loop connecting the C-terminal helix. The N-terminal domain of BpHldC is attached to the main catalytic domain by forming hydrophobic core consisting of Leu15, Ile55, Val95, Leu105, and Val109. The C-terminal helix domain seems to be connected to the main catalytic domain by a hinge loop in the superfamily -, 762349 2.7.7.70 additional information the N-terminal domain I spans amino acids 1-318 and shares structural features with members of the ribokinase family. The C-terminal domain II, which spans amino acids 344-477, has all the conserved features of the cytidylyltransferase superfamily 700026