Figure 2.

Structure of MsuD from P. fluorescens.A, MsuD adopts a classic (β/α)₈ barrel (green) with four insertion regions, labeled IS-1 (blue), IS-2 (red), IS-3 (orange), and IS-4 (gray). The extended protein C terminus is colored black. FMN (cyan) and MS⁻ (magenta) are displayed as sticks. B, MsuD adopts a dimer-of-dimers between chains A and B and chains C and D. Protein chains are labeled A–D and colored green, blue, yellow, and gray, respectively. C, the dimer and D, tetramer interfaces are displayed with labels for only half of the symmetrical interfaces for clarity. Hydrogen bonding networks are drawn as yellow dashed lines.