FIGURE 7.

Model of the complete hetero-octameric DPOR and distance between cofactors. Left, a qualitative, theoretical model of the complete DPOR was created by combining the heterotetrameric (ChlN/ChlB)₂ core complex from T. elongatus (this study) and ChlL₂ from R. sphaeroides (PDB code 3FWY) (16), based on the crystal structure of hetero-octameric nitrogenase (PDB code 1G21) (54). ChlN (ChlN′) and ChlB (ChlB′) are shown in shades of green (partly transparent), ChlL₂ is shown in shades of blue. Note the good surface complementarity between the subcomplexes. Right, the cofactors and the substrate of DPOR derived from the models on the left and Fig. 5 are shown in stick or ball-and-stick representation. Edge-to-edge distances are indicated in Angstroms, and distances from theoretical models are indicated by asterisks.