Optimization of Met8p crystals through protein-storage buffer manipulation

Sirohaem, the prosthetic group of assimilatory sulfite and nitrite reductas es, is a modified tetrapyrrole that belongs to the same fraternity of metal lo-prosthetic groups as haem, chlorophyll, cobalamin and coenzyme F430 [War ren & Scott (1990), Trends Biochem Sci. 15, 486-491]. In Saccharomyces cere visiae, the last step in the biosynthesis of sirohaem involves Met8p, a bif unctional enzyme responsible for both the NAD(+)-dependent dehydrogenation of the corrin ring and ferrochelation. Optimization of the protein storage buffer according to the results of crystallization trials resulted in a mor e monodisperse protein solution. Crystals were grown that diffracted to 2.1 Angstrom.