Pyridoxal 5'-phosphate-dependent methionine gamma-lyase (MGL) is involved in the metabolism of sulfur-containing amino acids. The enzyme is a promising target in some anaerobic pathogens and is effective in cancer-cell treatment. The structure of the MGL holoenzyme from Citrobacter freundii has previously been determined at 1.9 A resolution. By modification of the crystallization procedure, the previously determined structure of C. freundii MGL has been improved to 1.35 A resolution with R and R(free) values of 0.152 and 0.177, respectively. This high-resolution structure makes it possible to analyze the interactions between the monomers in detail and to reveal the structurally invariant regions that are responsible for monomer-monomer recognition during the formation of the active enzyme. Details of the mode of cofactor binding and of the flexible regions that may be involved in substrate recognition and binding are also described.