Stabilization of the structure of horse plasma vitamin D binding protein by disulfide bonds.

The research article is about a study which identified a way to stabilize the structure of horse plasma Vitamin D binding protein (DBP) through the use of disulfide bonds. The findings suggest a specific heating process can enhance the protein purification process without altering the end product.

Research Background and Methodology

• The researchers aimed to isolate Vitamin D binding protein (DBP) from horse plasma. DBP is a particular protein responsible for binding to and transporting Vitamin D in the bloodstream.
• Their technique involved a four-step procedure that utilized Affi-Gel Blue affinity chromatography, gel filtration, hydroxylapatite chromatography, and anion-exchange high-pressure liquid chromatography.
• From 80 mL of plasma, they extracted around 6 to 7 mg of DBP.

Characterization of DBP

• DBP from horse plasma was found to be very similar to other types of plasma DBPs. It was recognized as a tryptophan-free protein of Mr 53,000, meaning it doesn’t include the amino acid tryptophan and has a relative molecular mass of 53,000.
• It was found to be capable of binding to and inhibiting the polymerization of monomeric actin, an essential protein for muscle contraction and cell movement.
• The secondary structure of DBP was calculated based on circular dichroism measurements, revealing that it consists of 39% alpha-helix, 42% beta-sheet, and 19% random coil.

Role of Disulfide Bonds in DBP

• Circular dichroism and fluorescence studies were used to understand the role of the disulphide bonds within the DBP.
• The studies found that the disulfide bonds provide substantial stabilization to the structure of the DBP, particularly when it comes to thermal denaturation, or breakdown under heat.

Implications for Protein Purification

• The thermal stability of DBP revealed through these studies suggests a new method of purification: by incorporating a brief treatment at 70 degrees Celsius during purification, one chromatographic step can be left out.
• Notably, omitting this step doesn’t alter the end product, suggesting a more efficient means of DBP purification.