Crystallization and preliminary X-ray crystallographic analysis of Mirabilis antiviral protein

Mirabilis antiviral protein is a single-chain ribosome-inactivating protein purified from the tuberous root of Mirabilis jalapa L. We obtained several forms of crystals of the protein by the hanging drop vapor diffusion method, but most of these crystals were not suitable for X-ray crystallography. After refining the growth conditions, crystals of Crystallographic quality were grown in 20-μl droplets of an equi-volume mixture of 1.5% ( w v ) protein solution and a reservoir solution containing 49 to 50% ( w v ) ammonium sulfate and 50 m m-ammonium citrate (pH 5.4) at room temperature. Addition of 2 m m-adenine sulfate reduced twinning and “crystal shower”. The resulting trigonal crystals diffract beyond 2.5 Å resolution using a rotating anode X-ray generator. The space group was determined to be P3 121 or P3 221 ( a = b = 103.9 A ̊ , c = 134.6 A ̊ , α = β = 90 °, γ = 120 °) based on their precession photography of h0 l and hk0 zones. There seems to be three monomers in an asymmetric unit for V M = 2.51 A ̊ 3/Da .