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Figure 1.
The MtaBC structure. (A) In the (MtaBC)[2] heterotetramer (in
stereo) each MtaBC unit (MtaB in blue and MtaC in red) is
related to its partner unit (in light blue and red) by a twofold
noncrystallographic axis. The (MtaBC)[2] complex has a size of
62 Å × 55 Å × 52 Å and forms two
active sites separated by a distance of 38 Å. The
corrinoids are shown as stick models, and the zinc(II) ions are
depicted by green spheres. The contact loops between the two
active sites are highlighted in black. For oligomeric assembly
the interactions between the N-terminal extension of MtaC (in
green) and the counter MtaB are essential. (B) In the MtaBC unit
the Rossmann domain (orange) of MtaC is only loosely associated
with its helical domain (red) and MtaB (blue). MtaB is
subdivided into a TIM barrel core (dark blue) and a helical
layer (light blue). The active site is located between the
corrinoid cobalt and zinc(II).
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