M-PER Mammalian Protein Extraction Reagent From Pierce

The M-PER extraction reagent has been used in our laboratory for the isolation of proteins from mammalian cells (e.g. hepatocytes/adherent hepatoma cells) as well as insect tissues (e.g. mosquito midguts and salivary glands) prior to analysis by SDS-PAGE and downstream immunoblotting. The manufacturer’s instructions indicate that cell lysis is rapid and that freeze/thaw cycles and sonication are not required for the isolation of proteins. We can confirm that these statements are true; however, we’ve found that depending on the protein target of interest, these additional steps definitely help in the isolation. Cytosolic proteins are very easily solubilized using M-PER following the manufacturer’s instructions. However, in general, cytosolic proteins are always easier to solubilize compared to membrane proteins. Membrane protein isolation definitely requires the addition of non-ionic or zwitterionic detergents to M-PER. Since M-PER lysis of cells is a mild process, the proteins are maintained in their native state allowing for easy purification by immunoprecipitation and other methods. This is a definite advantage of this system. Furthermore, the M-PER reagent is compatible with the highly useful BCA assay (Pierce) for determining protein concentration.

The use of this buffer has been extremely useful to our laboratory in the past, since the formulation is “ready-to-go’, stable for months and allows for speedy isolation of proteins (once again depending on the proteins of interest). It provides a good base buffer formulation that allows you to increase your protein solubilization success by the addition of other mild detergents, e.g. non-detergent sulfobetaines (NDSB) or CHAPS. The reagent is by no means inexpensive and in this poor NIH funding climate, the purchase of such a reagent, while extremely useful, may not be necessary. In our hands, we have found that a 25 mM Bicine (N,N-Bis(2-hydroxyethyl)glycine) zwitterionic buffer works in the same capacity as the M-PER reagent under the same conditions and for the same applications that we have used M-PER in the past. The purchase of bulk detergent from Sigma Aldrich provides the laboratory with enough bicine buffer for years to come at a fraction of the cost for a 25 ml bottle of M-PER. The laboratory wishing to use M-PER should consider the use of the 25 mM bicine, 50 mM NaCl (pH 7.6-7.7) buffer supplemented with additional zwitterionic NDSB/CHAPS detergents and protease inhibitors if funding is tight. Bicine buffer is also compatible with the BCA assay. Since the technical difficulty of adding a sonication step or 1-2 freeze/thaw cycles to the isolation procedure is minor, we have opted to discontinue the use of M-PER in the lab.