One-step Negative Chromatographic Purification of Helicobacter pylori Neutrophil-activating Protein Overexpressed in Escherichia coli in Batch Mode

The overall goal of this purification is to yield functional Helicobacter pylori Neutrophil-activating protein or HP-NAP in its native form with high purity and high yield using negative mode batch chromatography with di-ethyl amino-ethyl ion exchange resin. The main advantage of this technique is that HP-NAP can be purified in its native form in one step with high purity and high yield. Negative purification of HP-NAP starts with a batch binding procedure in which the soluble protein fraction from bacterial lysates is added to DEAE resin.

The mixture is incubated to allow wholesale proteins to bind to the resin. HP-NAP present in the unbound fraction is then obtained by centrifugation of gravity flow. The implications of this technique is 10:1 prevention treatment and prognostic of Helicobacter pylori associated diseases as well as cancer therapy.

Because of the immunogenic and immunomodulatory properties of HP-NAP. Generally, individuals new to this method will struggle. Because HP-NAP easily aggregates during the sterilization.

Demonstrating the procedure will be Zhi-Wei Hong, a graduate student from our lab. Working at four degrees Celsius, we suspend 50 milliliters of the cell palate prepared as described in the text protocol in 20 milliliters of low salt, tris-buffer at pH 9.0 with protease inhibitor mixture. It's critical to keep sample at the four degrees Celsius to allow the procedure to prevent the protein aggregation.

Disrupt the bacterial cells by passing the bacterial suspension through a high-pressure homogenizer operated at a range of 15, 000 to 20, 000 PSI for seven times at four degrees Celsius. After lysates baterializes, it should be centrifuged immediately. Transfer homogenized samples to a centrifuge tube.

Immediately centrifuge the cell-lysate at 30, 000 times G at four degrees Celsius for one hour to separate the soluble and insoluble protein fractions by using an ultra-centrifuge. Following centrifugation, transfer the supernatant as the soluble protein fraction to a beaker. Measure the protein concentration of the soluble protein fraction by the Bradford method using a commercial kit with bovine serum albumin as the standard according to the manufacturer's instructions.

Then add 177.6 microliters of one normal HCl into 20 milliliters of the soluble protein fraction to adjust its pH value from pH 9.0 to pH 8.0. Add 20 millimeter Tris-HCl, pH 8.0, 50 milliliter sodium chloride to the protein solution to result in a final protein concentration of 0.5 milligrams per milliliter. To prepare 15 milliliters of DEAE resin, suspend 0.6 grams of DEAE resin dry powder in 30 milliliters of Tris-HCl buffer at room temperature for at least one day.

Centrifuge the resin at 10, 000 times G at four degrees Celsius for one minute and then remove and discard the supernatant. Then add 15 milliliters of Tris-HCl buffer. After repeating the centrifugation resuspension steps four more times, store the 15 milliliters of settled resin at four degrees Celsius for subsequent use.

Working at four degrees Celsius, add 45 milliliters of the prepared soluble proteins to milliliters of the resin and transfer to a 100 milliliter beaker with stir bar. Stir the protein resin slurry using a stir plate at four degrees Celsius for one hour. Next, pour the protein resin slurry into a plastic or a glass column fitted with a stopcock and allow the resin to settle under gravity.

Open the stopcock to allow the protein solution to run through the column by gravity flow until the liquid level in the column is just above the resin. Collect the flow through as the unbound fraction which contains the purified neutrophil-activating protein. Add 15 milliliters of the ice-cold Tris-HCl buffer into the column.

Open the stopcock again to allow the wash buffer to run through the column by gravity flow until the liquid level in the column is just above the resin. Collect the flow through as the wash fraction. Repeat washing with ice-cold buffer four more times to collect the additional wash fractions.

Then add 15 milliliters of ice-cold 20 millimeter Tris-HCl pH 8.0, one molar sodium chloride into the column. Collect the flow through as the elution fractions as before. Repeat the elution steps four more times to collect the additional elution fractions.

The effect of pH on solubility of HP-NAP in E.coli lysate are shown here. The amount of HP-NAP detected in this soluble fraction was markedly increased at pH 7.5 to 9.5. Recombinant HP-NAP was almost fully recovered in the soluble fraction upon cell lysis at pH 9.0.

Here, the effect of pH on negative purification of recombinant HP-NAP expressed in E.coli by DEAE resins in batch mode are shown. At pH 8.0, only a little amount of HP-NAP was present in the elution fraction. The amount of HP-NAP present in the unbound fractions was the highest at pH 8.0.

The optimized amount of proteins loaded onto the DEAE resin is 1.5 milligrams of protein per milliliter of resin for achieving maximum capacity of the resin to absorb the impurities from E.coli. At pH 8.0, very few proteins other than HP-NAP in its native form are recovered in the unbound fraction using DEAE resins in batch mode. The purity of HP-NAP was higher than 95 percent.

The purified HP-NAP folds into a multimer with a secondary structure of alpha-helix as revealed by the gelifiltration chromotogram and the far UV circular dichroism spectrum. A luminal dependent chemiluminescence assay reveals that the purified HP-NAP is able to trigger the production of reactive oxygen species by neutrophiles. Once mastered, these techniques can be done within five hours if it is performed properly.

After watching this video you should have a good understanding of how to purify functional HP-NAP in its native form with high yield and purity using negative mode batch chromotography with DEAE and exchange resin. While attempting this procedure, it's important to remember to use buffers at the appropriate pH in the step of sterilizes in the batch chromotography. We first had the idea for this method when we tried to apply other chromotographic approaches instead of filtration to purify HP-NAP in its native form.

Though this method is designed to appeal by recombinant HP-NAP expressed in E.coli. It can also be applied to other bacterial expression systems such as per-sida sep-tidas. Visual demonstration of this measure is quick code.

Plus the step of sterilizes and batch chromotography are difficult to learn. Because these steps must be carried out at the four degrees Celsius without any time delay. If a protein designed for purification is suitable for our exchange chromotography in negative mode, this procedure could also be adapted as a starting point for the development of purification process.

After its development, this technique paved the way for researchers in the field of clinical research to explore the possibility of using HP-NAP in cancer therapy as well as the development of vaccines, drugs, and the diagnostics for Helicobacter pylori associated disease.