BIO 121 Lecture Notes - Lecture 8: Copii, Signal Peptidase, Tunxis Community College

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coralimpala133

23 Nov 2020

School

Tunxis Community College

Department

Biology

Course

BIO 121

Professor

Quilty

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Document Summary

Membrane proteins: orieentation of membrane protein is determined when the protein is first inserted into the membrane, begin translation through membrane when start sequence is encountered, Are hydrophobic and consist of 8-10 non polar aa. N terminal start sequence: sequence remains in the membrane and is cleaved off of the protein after transfer through the membrane. Internal start sequence: binds to the srp and initiates transfer. Unlike the n-terminal signal sequence, it is not cleaved after transfer of the protein. Budding and fusion of vesicles maintains orientation of protein without risk of protein entering cytosol: experiemntal methods for determining endomembrane system, visual: microscopy. Centrefuge for weight to separate ribosomes, mitochondria etc: development of temperature sensitive secretion (sec) mutants in yeast. Removal of gene and see what happens. A temperature-sensitive mutation is one in which the protein sequence is affected by the change in dna sequence, but its not so severe that the protein is non-functional.

Related Questions

please help me answer theses questions correctly

1/ Which of the following are required for one-pass transmembrane proteins?

I. N-terminal signal sequence

II. Binding of SRP to the SRP receptor

III. Presence of stop-transfer sequence

IV. Presence of start-transfer sequence

a) I and III

b) I, II, and III

c) II, III, and IV

d) I, II, III, and IV

___________________

2/ Which of the following statements about the signal-recognition particle (SRP) is FALSE?

a) The SRP binds to the ER signaling sequence after the entire protein has been translated by the ribosome.

b) The SRP cycles between the ER membrane and the cytosol.

c) The SRP is required for peptides destined for either the ER membrane or ER lumen.

d) The SRP recognizes the signal sequence at the N-terminus of the newly forming polypeptide.

______________________

3) t-SNARES are _____.

a) found on the cytosolic side of the vesicle membrane.

b) necessary for recognition and transport of proteins into the nucleus.

c) usually located on the target membrane.

d) necessary for vesicle formation.

ceruleanchimpanzee878

1.. Protein X has a single N-terminal ER signal sequence, while protein Y has a single internal ER signal sequence. Which of these two proteins will be found in the ER lumen (Answer "X" or "Y")?

2. Protein A has an N-terminal ER signal sequence and one stop transfer sequence, while Protein B has an internal ER signal sequence and one stop transfer sequence. Which of these two proteins will have two transmembrane domains once its translocation is complete (Answer "A" or "B")?

3. What is the difference between an N-terminal ER signal sequence (SS) and an N-terminal mitochondrial SS?

a) the ER SS is an alpha helix, while the mito SS is a beta strand

b) the ER SS is a beta strand, while the mito SS is an alpha helix

c) the ER SS is an amphipathic alpha helix, while the mito SS is a hydrophobic alpha helix

d) the ER SS is a hydrophobic alpha helix, while the mito SS is an amphipathic alpha helix

4. True or False: ER stop transfer sequences and mitochondrial stop transfer sequences have similar characteristics.

5. True or False: Unlike translocation of proteins into mitochondria, translocation of proteins into the ER does not require energy.

scarletdog838