Please answer part 1 62. You are working in a lab studying trans-membrane protei
ID: 11306 • Letter: P
Question
Please answer part 1
62.You are working in a lab studying trans-membrane proteins and have been able to purify a protein that
the lab has been interested in for a long time. You conclusively show the protein is an integral membrane
protein with the COOH terminus located inside the cell and the NH2 terminus on the outside. You also
clone the gene encoding this protein. You lab director singles you out for praise saying “Your ambition is
exceeded only by your talent”. Great things are now expected of you. Your next experiment is to examine
the distribution of the protein by fluorescence microscopy. Briefly state how you would specifically
visualize this protein using this technique. <----PART 1
Now you examine the fluidity of this protein in the membrane using fluorescence recovery after
photobleaching (FRAP). Imagine you have a way to examine this protein in living cells (like one of the
possible approaches to the first part of the question). You perform FRAP on cells expressing either the
intact protein or a mutant version that lacks the COOH terminus (which is the part within the cytoplasm).
The graphs below show the results of the FRAP experiment; which protein shows more mobility in the
membrane (NORMAL or MUTANT )? Recalling how cells can regulate membrane protein mobility,
what is a likely hypothesis for why the mutant lacking the COOH terminus shows a different mobility
relative to the intact protein?
Explanation / Answer
Haha, I definitely just answered this! :) The COOH terminus is required to "end" the protein chain. COOH is carboxyl, a key amino acid building block of proteins. Think of the protein as a house - the protein is now without a roof, and a house without a roof is useless.