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Hi, can anyone explain protein expression.Please its very important

Hi,

Please can anyone help me understand this science paper on protein purification.

Maltose binding protein facilitates high-level expression and functional
purification of the chemokines RANTES and SDF-1a from Escherichia coli

Abstract
The chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and SDF-1alpha (stromal cell-derived factor-1alpha) are important regulators of leukocyte trafficking and homing. Chemokines form insoluble inclusion bodies when expressed in Escherichia coli (E. coli), resulting in low yields of soluble protein. We have developed a novel chemokine expression system that generates a high amount of soluble protein and uses a simple purification scheme. We cloned different types of RANTES and SDF-1alpha fused to either maltose binding protein (MBP) or glutathione-S-transferase (GST) and expressed the fusion proteins in E. coli under various conditions. We found that the yield of soluble chemokine is influenced by the type of fusion partner. Fusion to MBP resulted in a higher yield of total and soluble chemokine compared to GST. Under optimized conditions, the yield of soluble MBP-RANTES and MBP-SDF-1alpha was 2.5- and 4.5-fold higher than that of the corresponding GST-fusion protein, respectively. Recombinant chemokine fusion proteins exhibited specific binding activity to chemokine receptors. These results demonstrate that the use of MBP-fusion proteins may provide an approach to generating high yields of soluble and functional chemokines, such as RANTES and SDF-1alpha.



Any help will be appreciated.Thanks
Woah, that looks like one hell of a paper to understand, it gives me nightmares. But for that I would be revising on non-competitive enzyme inhibition and allosteric sites which reduce function. Also it is fully about the immune system so you would want to understand your major histocompatibility complexes pretty well. I would be going onto PDB or BLAST and checking out the peptidase and this SDF molecule, its way above my head at the moment sorry I cant really help. Good Luck though.
This is a common method of protein purification, known as affinity chromatography/purification. In essence you express recombinant protein with a "purification tag" fused to it. In this case the tags used are maltose-binding protein (MBP) and glutathione-S-transferase (GST), but other common ones include hexahistadine, FLAG, myc, SBP, HA.

You then mix the tagged protein with beads that have a ligand on them. In this case, the ligand for MBP is amylose, and the ligand for GST is glutathione. So now the protein we want is bound specifically to the beads. We wash away any unbound protein. Then we need to elute the protein we need off the beads, which we do so by adding an excess amount of ligand (maltose for MBP, and glutathione for GST). Then we should have purified protein.

This diagram explains it well:



Fusion tag (red) = MBP or GST
Affinity Ligand (green) = amylose or glutathione
elution ligand (blue) = maltose or glutathione
Target protein (orange) = RANTES and SDF-1a

Hope this helps!

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