Soybean hydrophobic protein. Isolation, partial characterization and the complete primary structure.

Area of Science:

• Plant biochemistry
• Protein characterization
• Glycine max research

Background:

• Soybean seeds contain numerous proteins, but novel ones with unique properties require detailed investigation.
• Understanding seed protein composition is crucial for agricultural and nutritional science.

Purpose of the Study:

• To isolate, characterize, and fully sequence a novel protein from soybean seeds.
• To investigate the physicochemical properties and potential physiological role of this newly identified protein.

Main Methods:

• Isolation of a 9000-Mr protein from a 60% ethanolic soybean seed extract.
• Protein sequencing, amino acid composition analysis, and disulfide bond determination.
• Crystallization, solubility tests, and aggregation studies under denaturing conditions.
• Homology search using computer analysis.

Main Results:

• A 9000-Mr protein comprising 80 amino acid residues with four disulfide bonds was identified.
• The protein is highly hydrophobic, lacks specific amino acids (methionine, phenylalanine, tryptophan, lysine, histidine), and aggregates under denaturing conditions.
• Sequence analysis revealed a hydrophobic amino-terminal region and a hydrophilic carboxyl-terminal segment.
• Unexpected homology to rat prolactin was detected, suggesting a potential new protein family.

Conclusions:

• A novel, highly hydrophobic soybean protein with unique structural features has been fully characterized.
• The protein's abundance and structural characteristics suggest a potential physiological role in plants, although no biochemical activity was detected.
• Further research is needed to elucidate the function and significance of this protein and its homology to rat prolactin.