Purification and crystallization of human cathepsin D

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Human cathepsin D is a key aspartic protease involved in protein degradation.
• Previous purification methods for aspartic proteases often rely on pepstatin affinity chromatography.
• Understanding the structure of cathepsin D is crucial for its functional and pathological studies.

Purpose of the Study:

• To purify the two-chain form of human cathepsin D from human spleen.
• To obtain high-quality crystals of human cathepsin D suitable for X-ray diffraction analysis.
• To determine the crystal structure of human cathepsin D.

Main Methods:

• Purification involved ion exchange chromatography followed by pepstatin affinity chromatography.
• Crystallization was achieved using the hanging drop vapor diffusion method with polyethylene glycol 8000.
• X-ray diffraction data were collected from seeded crystals.

Main Results:

• The two-chain form of human cathepsin D was successfully purified.
• Crystals of human cathepsin D were obtained and diffracted to 3.2 Å resolution.
• The crystals belong to space group P2(1)2(1)2(1) with specific unit cell dimensions, and two molecules occupy the asymmetric unit.

Conclusions:

• A robust method for purifying and crystallizing human cathepsin D was established.
• The crystallographic data provide a foundation for detailed structural analysis of human cathepsin D.
• This structural information can aid in understanding cathepsin D's role in biological processes and disease.