5. You have isolated two mutants of a normally pear-shaped microorganism have lo

Question

5. You have isolated two mutants of a normally pear-shaped microorganism have lost their distinctive shape and are now round. One of the mutants has a defect in a protein you call A and the other has a defect in a protein you call B. First, you grind up each type of mutant cell and normal cells separately and separate the plasma membranes from the cytoplasm, forming the first cell extract. Then you set aside a portion of each fraction for later testing. Next, you wash the remaining portion of the membrane fractions with a low concentration of urea (which will unfold proteins and disrupt their ability to interact with other proteins) and centrifuge the mixture. The membranes and their constituent proteins form a pellet, and the proteins liberated from the membranes by the urea wash remain in the supernatant. When you check each of the fractions for the presence of A or B, you obtain the results given below. hat First cell extract After urea wash and centrifugation Membrane ytosol Membrane Supernatant Normal cells First, tell me if the following statements are consistent with your results. Explain your answer (a) Protein A is an integral membrane protein that interacts with B, a peripheral membrane protein that is part of the cell cortex (b) Protein B is an integral membrane protein that interacts with A, a peripheral membrane protein that is part of the cell cortex. (c) Proteins A and B are both integral membrane proteins. (d) The mutation in A affects its ability to interact with B.

Explanation / Answer

Ans is A is integral membrane protein which interact with B , peripheral membrane protein that is a part of cell cortex.

Mutation in A affect its ability to interact with A.

In first case we have separated plasma membrane from cytoplasm. In normal cell both are in membrane means membrane protein but mutation in both A and B involve release of B in cytoplasm means B is peripheral protein that release in cytoplasm.

In case 2 when we treat normal cell with urea the release of B in supernatant confirm that B is peripheral protein. But mutant A and B , B not release in supernatant means A lost its ability to interact with B and its release in supernatant also lost.

These both theory prove that above mentioned result.

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