Human liver cathepsin D. Purification, crystallization and preliminary X-ray diffraction analysis of a lysosomal enzyme.
The two-chain form of active cathepsin D, a glycosylated, lysosomal aspartic proteinase, has been isolated from human liver. Isoelectric focusing revealed two major species of enzyme that differed by approximately 0.2 pI unit. Crystals suitable for X-ray diffraction analysis were prepared from acidic solutions using precipitation with ammonium sulfate. The hexagonal crystals diffracted X-rays to beyond 3.1 A resolution and belonged to space group P6(1) (or P6(5)) with cell constants a = b = 125.9 A, c = 104.1 A, gamma = 120.0 degrees. The crystals likely contain two molecules in the asymmetric unit, giving a solvent content of 56% (v/w). Biochemical analysis of crystals indicated that both isoforms were present in approximately equimolar proportions. Full structure determination of the enzyme is underway.
Gulnik
S
S
Structural Biochemistry Program, PRI/DynCorp, NCI-FCRDC, Frederick, MD 21702.
Baldwin
E T
ET
Tarasova
N
N
Erickson
J
J
D002402:Cathepsin D / Q000737:chemistry / Q000302:isolation & purification / Q000648:ultrastructure*; D003461:Crystallography; D006801:Humans; D007526:Isoelectric Point; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D014961:X-Ray Diffraction
D002402:Cathepsin D