Structure of a putative molybdenum-cofactor biosynthesis protein C (MoaC) from Sulfolobus tokodaii (ST0472).

The crystal structure of a putative molybdenum-cofactor (Moco) biosynthesis protein C (MoaC) from Sulfolobus tokodaii (ST0472) was determined at 2.2 A resolution. The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 123.31, b = 78.58, c = 112.67 A, beta = 118.1 degrees . The structure was solved by molecular replacement using the structure of Escherichia coli MoaC as the probe model. The asymmetric unit is composed of a hexamer arranged as a trimer of dimers with noncrystallographic 32 symmetry. The structure of ST0472 is very similar to that of E. coli MoaC; however, in the ST0472 protein an additional loop formed by the insertion of seven residues participates in intermonomer interactions and the new structure also reveals the formation of an interdimer beta-sheet. These features may contribute to the stability of the oligomeric state.