Figure 2.

Stereo plot of the barrel fold of F₄₂₀-dependent methylenetetrahydromethanopterin reductase from Methanosarcina barkeri in the monomeric form. The (αβ)₈ barrel core is presented in gray. Insertion regions (IR) are indicated in green (IR1 and IR3) and in blue (IR2). IR1 and IR3 consist mainly of helix α4-1 and the helical subdomains α7-1–α7-5, respectively. IR2 is composed of a β-hairpin like segment between α4 and β5. These insertion regions have important functions in either binding of F₄₂₀ (illustrated in red) and methylene-H₄MPT (not shown) or in forming the interface between the subunits. This stereoplot was prepared with PYMOL (DeLano Scientific LLC).