recombinant protein vs native protein - (Apr/11/2015 )

im reading a paper where they investigate the binding sites of eIF3, in one of the experiments they mutated the stem loop structure at a vicinity on mrna found to interact with eif3 to see the importance of the secondary structure for eif3 binding.  however they use a recombinant eif3 expressed from e.coli cells and they use native eif3 from hek cells. Why would they use recombinant eif3, what is the significance? i don't understand because it wasn't mentioned why in the paper. please help thanks

Engineering cells to produce your protein of interest has many advantages, even though it can be challenging and the protein may be translated differently thus affecting it's function.  E. coli is a very good host organism because they are easy to grow, they grow quickly, they are easily transformed, etc. 

MOST importantly though, if the stem-loop structure is mutated then the transgene has to be reintroduced back into a host.  My thoughts are that maybe hek cells are difficult to transform, unnecessarily expensive, not ideal to manage/store, honestly I don't know.  Maybe they use recombinant elF3 and native elF3 to compare and confirm that the eiF3 binding ability is unchanged.

E. coli is a great host and is a great model organism to start with if you are interested in a certain protein.