Crystallization and preliminary X-ray diffraction analysis of two lysinal derivatives of Achromobacter protease I

Two crystal forms of lysinal derivatives of Achromobacter protease I have been obtained. The first, modified by benzyloxycarbonyl-Val-lysinal crystallizes in the monoclinic space group P2₁ with unit-cell dimensions of a = 39.6, b = 71.2, c = 45.6 Å and β = 98.4°. The second, modified by benzyloxycarbonyl-Leu-Leu-lysinal crystallizes in the orthorhombic space group I222 (or I2₁2₁2₁) with unit-cell dimensions of a = 98.7, b = 102.2 and c = 55.8 Å. The space groups and the unit-cell dimensions of the present two lysinal derivatives are different to those of the protease and TLCK- modified one. The space group of the protease is P1 with cell dimensions a = 39.53, b = 40.34, c = 43.92 Å, α = 114.81, β = 113.75 and γ = 74.00° and that of the TLCK-modified one is also P1 with cell dimensions of a = 37.30, b = 42.74, c = 48.02 Å, α = 120.10, β = 112.81 and γ = 68.54°. Diffraction to 1.9 Å resolution for the Val-lysinal modified crystal and to 2.2 Å resolution for the Leu-Leu-lysinal modified crystal has been observed using a rotating-anode X-ray generator. Full structure determinations of these lysinal-modified protease crystals may lead to an understanding of the molecular basis of enzyme–substrate interactions in the catalytic process of this protease.