Figure 6: Structure of the ternary complex CyaY/IscS/IscU.

(a) Surface representation of the model obtained by combining the small-angle X-ray scattering and NMR information, showing in blue and cyan the two IscS protomers; in red and orange red, IscU; and in gold and yellow, CyaY. (b) Surface representation in the same orientation as in (a) of the IscS complex (blue and light blue) with TusA⁹ (different gradations of green, 3LVJ). (c) Blowup of Figure 6a but in a ribbon representation showing the relative position of pyridoxal phophate (PLP, magenta), the catalytic loop (purple), the three conserved cysteines of IscU (yellow) and Trp61 of CyaY (green). The catalytic loop was built by homology using the 3GZC47 coordinates the sequence of which has a sequence similarity/identity of 30 and 50%, respectively, and superposes to 1P3W, with a lower root mean square deviation of 1.21 Å. The resulting model was energy minimized by the Gromacs package⁵⁵.