Influence of the presence of the heme cofactor on the JK-loop structure in indoleamine-2,3-dioxygenase-1

Indoleamine 2,3-dioxygenase 1 has sparked interest as an immunotherapeutic
target in cancer research. Its structure includes a loop, named the JK-loop, that
controls the orientation of the substrate or inhibitor within the active site.
However, little has been reported about the crystal structure of this loop. In the
present work, the conformation of the JK-loop is determined for the first time in
the presence of the heme cofactor in the active site through X-ray diffraction
experiments (2.44 A ˚ resolution). Molecular-dynamics trajectories were also
obtained to provide dynamic information about the loop according to the
presence of cofactor. This new structural and dynamic information highlights the
importance of the JK-loop in confining the labile heme cofactor to the active
site.