A soybean trypsin inhibitor. Crystallization and x-ray crystallographic study

Area of Science:

• Biochemistry
• Structural Biology
• Crystallography

Background:

• Soybean seeds contain multiple low molecular weight trypsin and alpha-chymotrypsin inhibitors.
• These protease inhibitors play a role in plant defense mechanisms.

Purpose of the Study:

• To isolate and purify trypsin and alpha-chymotrypsin inhibitors from Tracy soybean seeds.
• To obtain single crystals of an inhibitor for X-ray diffraction analysis.
• To characterize the crystal structure and properties of a soybean trypsin inhibitor.

Main Methods:

• Isolation and purification of five low molecular weight inhibitors from soybean seeds.
• Crystallization of one trypsin inhibitor.
• X-ray diffraction analysis of the inhibitor crystal.
• Determination of unit cell dimensions and space group.

Main Results:

• Five inhibitors with molecular weights between 6800 and 8600 were isolated.
• A single crystal of a trypsin inhibitor was obtained, yielding X-ray diffraction data beyond 3-A spacings.
• The trypsin inhibitor crystallized in a monoclinic unit cell (P2(1)) with specific dimensions.
• The asymmetric unit contains one molecule of 6800 molecular weight.
• The crystal exhibited unusual stability to X-radiation with approximately 26% solvent content.

Conclusions:

• The study successfully isolated and purified multiple soybean seed inhibitors.
• Crystallographic data provided initial insights into the structure of a soybean trypsin inhibitor.
• The obtained crystal properties suggest potential for detailed structural studies.