My gene of interest is toxic to bacterial cells. Are there any precautions you can suggest?
Several precautions may be taken to prevent problems resulting from basal level expression of a toxic gene of interest. These methods all assume that the T7-based or Champion-based expression plasmid has been correctly designed and created.
- Propagate and maintain your expression plasmid in a strain that does not contain T7 RNA polymerase (i.e., DH5α).
- If using BL21 (DE3) cells, try growing cells at room temperature rather than 37 degrees C for 24-48 hr.
- Perform a fresh transformation using a tightly regulated E. coli strain, such as BL21-AI cells.
- After following the transformation protocol, plate the transformation reaction on LB plates containing 100 µg/mL ampicillin and 0.1% glucose. The presence of glucose represses basal expression of T7 RNA polymerase.
- Following transformation of BL21-AI cells, pick 3 or 4 transformants and inoculate directly into fresh LB medium containing 100 µg/mL ampicillin or 50 µg/mL carbenicillin (and 0.1% glucose, if desired). When the culture reaches an OD600 of 0.4, induce expression of the recombinant protein by adding L-arabinose to a final concentration of 0.2%.
- When performing expression experiments, supplement the growth medium with 0.1% glucose in addition to 0.2% arabinose.
- Try a regulated bacterial expression system such as our pBAD system.
I'm trying to express my protein using a bacterial expression system. How do I know if I'm seeing degradation of my protein or if what I’m seeing is codon usage bias?
Typically, if you see 1-2 dominant bands, translation stopped prematurely due to codon usage bias. With degradation, you usually see a ladder of bands. With degradation, you can try using a protease inhibitor and add it to the lysis buffer to help prevent degradation. If degradation is the issue, a time point experiment can be done to determine the best time to harvest the cells.
I'm trying to express my protein using a bacterial expression system and am getting inclusion bodies. What should I do?
If you are having a solubility issue, try to decrease the temperature or decrease the amount of IPTG used for induction. You can also try a different, more stringent cell strain for expression. Adding 1% glucose to the bacterial culture medium during expression can also help.
A multipurpose vector system for the screening of libraries in bacteria, insect
and mammalian cells and expression in vivo.
Authors:Laitinen OH, Airenne KJ, Hytönen VP, Peltomaa E, Mähönen AJ, Wirth T, Lind MM, Mäkelä KA, Toivanen PI, Schenkwein D, Heikura T, Nordlund HR, Kulomaa MS, Ylä-Herttuala S,
Journal:Nucleic Acids Res
PubMed ID:15731335
We have constructed a novel tetra-promoter vector (pBVboostFG) system that
enables screening of gene/cDNA libraries for functional genomic studies. The vector enables an all-in-one
strategy for gene expression in mammalian, bacterial and insect cells and is also suitable for direct
use in vivo. Virus preparation is based on an improved mini Tn7 transpositional ... More
Tomato aromatic amino acid decarboxylases participate in synthesis of the flavor volatiles 2-phenylethanol and 2-phenylacetaldehyde.
Authors:Tieman D, Taylor M, Schauer N, Fernie AR, Hanson AD, Klee HJ,
Journal:Proc Natl Acad Sci U S A
PubMed ID:16698923
'An important phenylalanine-derived volatile compound produced by plants is 2-phenylethanol. It is a major contributor to flavor in many foods, including fresh fruits, such as tomato, and an insect-attracting scent in roses and many other flowers. Despite the centrality of 2-phenylethanol to flavor and fragrance, the plant genes responsible for ... More
Identification of an antiangiogenic FGF2-binding site in the N terminus of the soluble pattern recognition receptor PTX3.
Authors:Camozzi M, Rusnati M, Bugatti A, Bottazzi B, Mantovani A, Bastone A, Inforzato A, Vincenti S, Bracci L, Mastroianni D, Presta M,
Journal:J Biol Chem
PubMed ID:16769728
'Long-pentraxin 3 (PTX3) is a soluble pattern recognition receptor with non-redundant functions in inflammation and innate immunity. PTX3 comprises a pentraxin-like C-terminal domain involved in complement activation via C1q interaction and an N-terminal extension with unknown functions. PTX3 binds fibroblast growth factor-2 (FGF2), inhibiting its pro-angiogenic and pro-restenotic activity. Here, ... More
Domain structure and DNA binding regions of beta protein from bacteriophage lambda.
beta protein from bacteriophage lambda promotes a single-strand annealing reaction that is central to Red-mediated recombination at double-strand DNA breaks and chromosomal ends. beta protein binds most tightly to an intermediate of annealing formed by the sequential addition of two complementary oligonucleotides. Here we have characterized the domain structure of ... More
Proteolytic processing of sapovirus ORF1 polyprotein.
The genome of Sapovirus (SaV), a causative agent of gastroenteritis in humans and swine, contains either two or three open reading frames (ORFs). Functional motifs characteristic to the 2C-like NTPase (NTPase), VPg, 3C-like protease (Pro), 3D-like RNA-dependent RNA polymerase (Pol), and capsid protein (VP1) are encoded in the ORF1 polyprotein, ... More