) You treat some cells with a proteolytic enzyme that is too large to penetrate the cell membrane (Set 1). Another group of cell
s is made permeable before treatment with the enzyme (Set 2). A third set of cells was not treated with the enzyme at all (controls). Proteins are then extracted from the three different sets of cells and applied to an SDS-PAGE gel. Protein W migrates to the same distance on a gel of proteins from Set 1 and Set 2; Protein W migrates a shorter distance on gels of proteins extracted from the control group than on gels of proteins extracted from Set 1 and Set 2 treated cells. Protein X migrates to the same distance on a gel of proteins from control cells and the gels of the proteins from Set 1 and Set 2. Protein Y migrates a longer distance when extracted from Set 1 cells than does protein Y in the controls; Protein Y moves an even larger distance in the gel of the extracts from Set 2. Protein Z migrates the same distance on gels of proteins from the controls and the proteins extracted from Set 1, but it migrates a longer distance in extracts from Set 2 cells. Which protein is exposed only on the exterior of the cell?
SDS-PAGE gel is a method used for the separation of proteins in which proteins are separated based on their length (smaller proteins move faster through the gel, due to less resistance).
When treated with proteolytic enzymes, proteins are cut and become short fragment. This means that the fragments formed after the use of proteolytic enzymes, will move faster and thus, migrate a longer distance. Proteolytic enzymes in Set 2 cells will act only on plasma membrane proteins (because they cannot penetrate), while in Set 2 they will act on both, plasma membrane and interior proteins. Control group will have only the large fragments (not treated with enzyme).
Protein W travels the same distance on a gel of proteins from Set 1 and Set 2, but different than control group. It means that the proteolytic enzyme worked the same on Set 1 and Set 2.
