Fig. 9. A stereodrawing of the fold of cobalamin-dependent methionine synthase (MetH) (1-566) from Thermotoga maritima. The N-terminal homocysteine (Hcy) barrel includes residues 1-291 and is linked by an intervening sequence to the folate (Fol) barrel that begins at residue 315. The view is approximately down the axis of the Hcy barrel and is oriented to show the hairpin component of the domain interface. Hcy and CH₃-H₄folate are included in space-filling mode. The shortening of strand 8 of the Fol barrel is evident near residue 540.