Preliminary X-ray diffraction studies of recombinant 19 kDa human fibroblast collagenase

Crystals of the catalytic domain of human fibroblast collagenase have been grown in the presence and absence of an inhibitor. Crystals of the inhibitor complex grew from 0.2 M ammonium sulfate and 15 to 30% PEG 8000 at 22 degrees C as bipyramids in the space group P6(2) or P6(4). Crystals of the unligated enzyme grew as rods in the space group P4(1)2(1)2 or P4(3)2(1)2 from 1.0 to 2.0 M sodium formate at 4 degrees C. Both crystal forms grew quite slowly over a period of months, but ultimately yielded crystals that diffracted beyond 2.5 A. The collagenase samples used in these studies were heterogeneous at the amino terminus. Three major species (full length, N-1 and N-2) were identified by mass spectrometry and Edman sequencing. Analysis of dissolved crystals revealed the native crystal form selectively crystallized as the N-2 species; however, no selectivity of N-terminal forms was observed for crystals of the inhibitor complex.