The process of Protein extraction would broadly follow tissue/cell lysis (extraction), precipitation and then purification. The step one may involve the use of blender, sonicator or a chemical method of enzymatic digestion. The goal is to pool out the proteins from the cell membrane via breaking the membrane. Cell lysis normally releases protease which may break down the protein of interest. In order to avoid this, protease inhibitors are used and next step is made quickly.
Many methods can be employed to precipitate the proteins out. One common way is to use Ammonium sulfate wherein the solubility of protein gets altered in presence of the high salt concentration. This method is also known as salting out since ammonium sulfate is a neutral salt. If a strong detergent like Sodium Dodecyl Sulfate (SDS) is used in the extraction step then most membrane proteins will precipitate upon removal of the detergent as membrane proteins are soluble in SDS. Miscible solvents like methanol and ethanol are also used for precipitation as their addition decreases the dielectric constant of water, which in turn allows two proteins to come close together and precipitate. By this point, the protein might have some Non-compacted particles which are removed as 'supernatant' through the process of centrifugation.
Many commercial kits offer reagents for quicker and easier protein extraction. Biomall offers a range of such kits along with all other reagents and solutions required in protein extraction procedures.