The most important factor for choosing a suitable host organism would be obtaining functional or active protein post expression. One example can be of Actin protein which needs a special enzyme to acetylate N terminal of protein present only in higher eukaryotes rendering bacterial and yeast systems useful to obtain actin protein. Some labs also use insect cell lines to make protein production a bit cost effective than directly going into mammalian expression systems like CHO or others. I hope this answers your query.

Insect expression platforms are inexpensive, Widely used for the production of recombinant proteins for structural studies, but less demanding than mammalian cells. Established insect cell lines may produce recombinant proteins with high yields and require smaller culture volumes.

Insect cell lines for recombinant protein production using the baculovirus expression vector system (BEVS) are Sf9 and Sf21 (Spodoptera frugiperda)

These cell lines are favored over prokaryotic systems because they are eukaryotic and can perform necessary post-translational modifications, resulting in more biologically relevant proteins.

Dear Gnana Sandeep Naraharisetti

As you suggest E. coli offers rapid growth and cost-effectiveness but lacks post-translational modifications teast and mammalian cells provide better folding and modifications but are slower and more expensive.

Moreover the production of stable cells in E.coli is quite easy since plasmid mantainance in E.coli could be guaranteed using a selection marker (as antibiotic resistance), is not so easy in yeasts and is difficult and time expensive in mammalian since the gene integration in genome and best clone selection is a long and expensive step.

There is not an universal best expression hosts. Do you need to select it on the basis of the:

- Sequence of the protein that you would like to produce;

Proteins with high MW or containing many cysteines involved in S-S may not be produced with proper folding and good yields in E.coli.

Proteins that require to be glicosilated for its function cannot be produced in E.coli

high mw proteins or hetermodimers as for example monoclonal antibodies are expressed with higher yields and proper folding from mammalian

- Scale of production (ug, mg or grams)

Production of ug or mg scale could be obtained in mammalian performing transient trasfection wtih is relativelly simple and modern cells

https://www.blogger.com/video.g?token=AD6v5dyTuEwDXD2ztCnLIFHkG06cCp1jaRuUHOGFtHdiTFnj-yS_TyCyPqzvi6RogJaSP_sXqbJnMDIYplkXODpfOc21BETPPh74J7FJuwMPxHW4X79mURcAl7-V0ApA8BQrGUAgcSc

and co-trasfection of 2 plasmid can allow to produce heterodimes ad the mab in simplest way respect than bacteria where co-expression is feasible but more complex.

https://proteocool.blogspot.com/2021/06/tips-of-week-8-expi-cho-powerful-cell.html

- Aim of production

Production of human antigens for immunization of antibody production is preferable in mammalian cells that are able to produce the same PMT and you obtain a protein more similar to the human or viral antigen

Production of bacterial antigens that do not need PMT is preferable in bacterial since mammalian may introduce some PMT that are not present in the reality

Production of 15N, 15N,13C oe 2H,15N,13C labelled proteins for structural studies still need to be performed using E.coli since labelling with mammalian is difficult and very expensive

https://www.blogger.com/video.g?token=AD6v5dwMieb--rE6-qY-WfM4fv8o-2PbxqaWuGxZ7_U3QB5tB113BQ1lEjHxpZhRMLWIWkeHmZV_LcuaESWuqDtZe1L3JI62cDvZaMQyL6BLVQxIRJtuE7IPw8SYCQHKWSV4_CCL0cs

Production of antibodies used in clinical trials need to be performed in cell lines approved for clinical use ad CHO and constructoon of a stable cell line is still mandatory to my knowledge to proceed with a phase 1 clinical study

good luck

Manuele