Question

In your membrane fraction that you gently isolated from the cell you have an enzyme activity that you are interested in studying. a. You need to determine if the protein is an integral or peripheral membrane protein. How would you determine this? a. What type of amino acids do you expect if the protein is an integral membrane protein? (list 2 specific amino acids and explain why) TT TT Paragraph Arial 3 (121)

Answer 1

1. If the protein is having an enzymatic activity that is present either on the peripheral or the integral part of the cell membrane then it is important to validate the location of the active protein present in the cell membrane. The NaCl which is the salt can be used for the separation of the cell membrane from the peripheral protein. Further, the centrifugation can be carried out and if the protein presence has been seen in the pellet then the protein can be said to be the integral protein in the cell membrane while if the protein is present in the supernatant then it can be seen to be the peripheral protein.

Ahead of this isolation, the protein can be checked for the enzymatic action by treating it with the substrate which binds to the protein and thus through the enzyme kinetics it can be found that which protein is shwoing the enzymatic activity and working as an enzyme.   

2. If it is the integral membrane protein then the negatively charged amino acid which can bind to the hydrophobic part of the lipid membrane can be seen in the protein which are either aspartic acid or the glutamic acid. While if the protein is present on the peripheral region then the binding of the protein has to take place on the hydrophilic head of the phospholipids and thus the positively charged amino acids such as the lysine and arginine or histidine can be seen to be present in the peripheral proteins.