At some point many researchers working not only strictly in proteomics but also in other fields such as genetics, cell biology, microbiology and so on, find themselves in need of a certain protein. While there is a great number of recombinant proteins that have already been developed and available in stock with the suppliers of life sciences products, the vast majority of discovered and studied proteins remain unavailable for a direct purchase. Luckily, there a lots of companies that offer custom protein expression services at very reasonable prices.
There are a few basic key features that you need to consider prior to placing your order. First and foremost, of course, is the protein’s sequence. Most providers of this service need only either a sequence or an uniprot number. Another thing to consider is the preferred expression system. Generally there are 4 types of host organisms that are used for producing recombinant proteins – Yeast, E.coli, Baculovirus and Mammalian cell lines. Each has its advantages, disadvantages and limitations. Next thing – choosing the proper Tag. The tag is mostly need for the purification of the protein from the cell culture. Some of the most common tags are Myc- and HIS-tag and they can be located in the N- or C-terminus of the protein. Most suppliers provide also a tag removal service but keep in mind that it is not successful in 100% of the times. One more thing to pay attention to – if your protein has a transmembrane domain – such proteins are extremely hard to express and generally should be expressed in a host organism similar to the origin species (e.a. a human/mouse/rat protein -> mammalian cell line; bacterial protein -> E.coli). Still the success of the expression of such proteins is questionable and almost entirely empirical. Last on this short list of basics is the endotoxin levels – if you will be using your protein, for example, in a living cell culture, it is highly recommended that you request for an endotoxin removal service, otherwise your cells might die.