Figure 4.

Superposition of ribbon diagrams of the D. desulfuricans (ATCC 29577) flavodoxin structures with two loop conformations with the D. vulgaris flavodoxin. The D. desulfuricans (ATCC 29577) flavodoxin structure with the straight (purple) and bent (cyan) Trp60-containing loop conformations shows (a) high similarity (r.m.s.d. 1.3 Å) to the D. vulgaris flavodoxin structure (PDB code 1azl; green). The major difference lies in the Trp60-containing loop. In (b) the structures are rotated to highlight the flexibility of the Trp60-containing loop. In all three structures the position of Trp60 (sticks) that coordinates the flavin mononucleotide is maintained. The atomic displacement parameters (ADPs) for the Trp60-containing loop are significantly higher than the overall ADP as shown in (c), a plot of the ADP by residue number for the P4₃ (blue), the P3₁21 straight-loop (magenta) and P3₁21 bent-loop (cyan) crystal structures, supporting the conclusion of loop flexibility.