1) What do you think would happen to an integral membrane protein that normally
ID: 84376 • Letter: 1
Question
1) What do you think would happen to an integral membrane protein that normally is localized to the plasma membrane, and has a N-terminal signal sequence and a long hydrophobic portion near the C-terminus, under each of the following conditions?
a) The gene that codes for the protein is mutated so it no longer has a signal sequence.
b) The gene that codes for the protein is mutated so it no longer has the long hydrophobic portion.
2) You accidentally washed off the labels off of 3 drugs you were using to treat cells. One of the drugs inhibited myosin, one of them inhibited kinesin, and one of them inhibited dynein. You picked one of the drugs at random and used it on some of his immune cells that normally secrete antibodies. When you analyzed the cells you saw that the cleavage furrow seemed to be working fine, the Golgi were forming fine, but the ER was not very spread out in the cells and the cells were unable to secrete any antibodies. Which drug you likely used?
Explanation / Answer
1a. There are 6 kinds of targeting sequences among which N-terminal sort for ER. A ribosome-associated signal recognition particle scans the nascent polypeptide chain as it emerges from the ribosome. if it encounters a hydrophobic N-terminal signal sequence, it binds it, and freezes movement of the ribosome along the mRNA. The ribosome:mRNA:SRP complex then binds to a receptor on the surface of the rough endoplasmic, whereupon protein synthesis resumes, and the proteins is co-translationally extruded through the membrane of the ER into the lumen of the ER. so if N-terminal signal sequence is muated ribosome-associated signal recognition particle may not be able to scans the nascent polypeptide chain as it emerges from the ribosome. Thus ribosome:mRNA:SRP complex may not able to form and does'nt allow a receptor on the surface of the rough endoplasmic to bind there by protein synthesis may not resumes. and protein may not able to extrude from ER to lumen of ER.
2. The motility and structure of ER was siverly affected by inhibition of mysoin. Thus, cells were treated with One of the drug which inhibited myosin.
1b. Rsidues with hydrophobic side chains in most integral proteins interact with fatty acyl groups of the membrane phospholipids, thus anchoring the protein to the membrane. so if protein is mutated and it is no longer has the long hydrophobic portion then it lacks the property to anchor to the membrane.
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