Structure of hypothetical Mo-cofactor biosynthesis protein B (ST2315) from Sulfolobus tokodaii

The structure of a probable Mo-cofactor biosynthesis protein B from Sulfolobus tokodaii, belonging to space group P6₄22 with unit-cell parameters a = b = 136.68, c = 210.52 Å, was solved by molecular replacement to a resolution of 1.9 Å and refined to an R factor and R_free of 16.8% and 18.5%, respectively. The asymmetric unit contains a trimer, while the biologically significant oligomer is predicted to be a hexamer by size-exclusion chromatography. The subunit structure and fold of ST2315 are similar to those of other enzymes that are known to be involved in the molybdopterin- and molybdenum cofactor-biosynthesis pathways.