(A) Surface representation of MTCYP51 structure. Heme,
shown in red, is accessible from the surface through the open mouth of
the substrate entry-channel 1. Surface was generated with
GRASP (35). (B) View of
substrate-binding site from the direction of the substrate entry along
channel 1. Gray ribbon represents the P450BM3 (31), and yellow
represents MTCYP51. Both structures were superimposed so that rms
deviation for the most structurally homologous regions is 1.15 Å. For
MTCYP51, regions of highest structural homology based on
SWISS-PDB VIEWER superimposition algorithm include
G41-R64, M110-C151, A256-L289, Q306-Y370, and W382-R448, which
correspond to regions F40-D63, M112-C156, A264-L297, Y313-F379, and
H388-K451 in P450BM3. MTCYP51 BC loop is open and lies above the N
terminus of the bent I helix, which is pulled away from the structural
core.