Crystallization and preliminary X-ray analysis of B-­domain fragments of a Staphylococcus aureus collagen-binding protein

Recombinant proteins of monomeric and dimeric B-domain repeats of a Staphylococcus aureus FDA 574 collagen-binding adhesin have been crystallized. The single repeat unit (B₁) was crystallized in a body-centered orthorhombic lattice with a = 96.9, b = 101.3, c = 120.8 Å in either the I222 or I2₁2₁2₁ space group. These crystals diffracted to 2.5 Å resolution and the calculated V_m values of 3.2 and 2.2 Å³ Da^-1 suggest the possibility of a dimer or a trimer in the asymmetric unit. The two-repeat fragment (B₁B₂) crystallized in the orthorhombic space group P2₁2₁2₁ with cell dimensions a = 42.4, b = 79.4, c = 130.4 Å and diffracted to 2.3 Å resolution. For this species, the calculated V_m value of 2.2 Å³ Da^-1 indicates the presence of a monomer in the asymmetric unit.