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Meet Protein Vector: A system that enables you to purify any protein!

Posted by Applied Biological Materials (abm) on May 22, 2019

This week's Vector and Virus Spotlight is on the Protein Vector, an expression system that can be tailor made for protein purification - a pure delight to work with! Learn about why protein vectors can be useful for your protein expression needs.

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Protein Vector Character


Meet Protein Vector

"Good to meet you! I’m Priscilla Vecchio. I may not have any viral packaging ability, but that makes me very easy to work with! Whether you want your gene expressed from mammalian or bacterial cells, I can help. I love to add a personal touch to your gene with tags, which can then be used to purify your protein!"



Overview

Protein vectors are a non-viral option for expressing protein to be purified. Protein vectors include a purification tag that will be fused to the gene of interest, making it easy to purify the protein once it is expressed. To prevent potential interference of the purification tag with normal protein function, some tags are able to be cleaved from the protein of interest using proteolytic agents such as thrombin or TEV protease.

Purification tags may be fused to either the C- or N-terminal of a protein, and can work in a variety of ways. Affinity tags allow for proteins to be purified using an affinity technique. Examples include maltose binding protein (MBP), glutathione-S-transferase (GST), and His tags. Epitope tags can be used to purify proteins using high-affinity antibodies which bind to them. Examples include HA tags, and FLAG tags (D tags). As well, certain tags may help the protein of interest to fold correctly and keep it from precipitating. These are called solubilization tags, and examples include MBP and GST.



Mammalian or Bacterial Expression?

Expression in mammalian and insect cells allow for post-translational modifications. Bacterial cells are easy to culture and can generate large quantities of protein.

When a mammalian gene is translated in mammalian cells, it will undergo all post-translational modifications that would occur in nature. Therefore protein produced in a mammalian system will be more authentic for experimental use than one produced in a bacterial system. However, mammalian cells are much more difficult and time-consuming to culture than bacterial cells. Therefore, for applications where large amounts of protein are required and authenticity is not a major concern, bacterial expression is a good choice. If large amounts of post-translationally processed protein are required, a baculoviral expression system should be considered.

For a transgene to be expressed in bacteria, it must be driven by a bacterial promoter. Common bacterial promoters that are used in protein vectors include T7 and Lac.

For a transgene to be expressed in mammalian cells, it must be driven by a mammalian promoter. Common mammalian promoters that are used in protein vectors include CMV, EF1a, CAG, and EF1a.



Choose a Protein Vector for mammalian expression if:
  • You need to purify large quantities of protein.
  • You do not require post-translational modifications to the protein.
  • You do not have the equipment to culture mammalian cells.
  • You do not wish to use a viral system.


Choose a Protein Vector for mammalian expression if:
  • You wish for your protein to have post-translational modifications.
  • You have the equipment to culture mammalian cells.
  • You do not want to use a viral system.


About abm's Protein Vectors

Looking to work with protein vectors? Have a look at our selection.

Key features of abm's protein expression vectors include:

  • Expression: The option for expression in either a prokaryotic (E. coli; T7 promoter based) or a eukaryotic (mammalian cell; CMV promoter based) system
  • Genes available: Human, Mouse, Rat
  • Tags: A choice of 5 tags (His, HA, MBP, GST and D-tag; some in combination) with both N-terminal and C-terminal options for a His tag


The below table can be used as a quick reference guide for determining what our different tags can offer:

Tag Name Description Size (kDa) Cleavable
C-His A single C-terminal 6X-Histidine tag 0.84 No
N-His A single N-terminal with 6X-Histidine tag 2.3<15 min Yes (with thrombin)
C-HA A single C-terminal Hemagglutinin tag 1.1 No
His-MBP Dual N-terminal tag; 6X Histidine followed by Maltose Binding Protein 43 Yes (with TEV)
His-GST Dual N-terminal tag; 6X Histidine followed by Glutathione-S-Transferase Protein 27.9 Yes (with TEV)
N-D-C-HA Dual tags; N-terminal 3X D-tag and C-terminal Hemagglutinin tag N: 3X
FLAG: 3.5
C-HA: 1.1
N: Yes (with TEV)
C: No
N-D-C-His Dual tags; N-terminal 3X D-tag and C-terminal 6X-Histidine tag N: 3X
FLAG: 3.5
C-His:0.84
N: Yes (with TEV)
C: No


Can't find your gene of interest or need a wider selection of tags? abm offers custom protein production services.



Don't know which viral vector to choose?

You know you want to express a gene, but when it comes time to choose an expression vector, your choices can seem overwhelming. Do you go viral or non-viral? Which virus should you use? Or maybe it's not a protein you need to express, but an RNA species?

Try using our Vector Selection Tool. Cut through the fog with this Vector Selection Tool. Simple, clear recommendations for every application.



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