BC 465 Exam 4

The cycle between Ran-GTP and Ran-GDP is modulated by:

a. Cytosolic Ran-GEF and nuclear Ran-GAP

b. Cytosolic Ran-GEF and Ran-GAP in the ER lumen

c. Cytosolic Ran-GAP and nuclear Ran-GEF

d. Cytosolic Ran-GAP and Ran-GEF in the ER lumen

c. Cytosolic Ran-GAP and nuclear Ran-GEF

A polypeptide starts folding into secondary structures:

a. During translation, at the P-site of ribosome

b. During translation, at the A-site of ribosome

c. During translation, after reaching the ribosomal exit tunnel

d. After being fully synthesized and released from the ribosome

c. During translation, after reaching the ribosomal exit tunnel

The main function of heat-shock protein family is to:

a. Induce transcription of proteins induced by heat shocks

b. Promote folding of proteins that do not fold by themselves

c. Prevent misfolding of proteins under cellular stress

d. Prevent translation of proteins induced by heat shocks

c. Prevent misfolding of proteins under cellular stress

The NF-AT transcription factor preferentially localizes to nucleus:

a. When cleaved by Delta-Notch signaling pathway

b. At low concentration of intracellular Ca2+ ions

c. Upon Calcineurin-mediated phosphorylation

d. Upon Calcineurin-mediated dephosphorylation

d. Upon Calcineurin-mediated dephosphorylation

Most nuclear proteins are synthesized in the:

a. Cytosol

b. Endoplasmic reticulum

c. Nucleus

d. Mitochondria

a. Cytosol

Nuclear export receptors preferentially bind to:

a. Nuclear Importins in their ATP bound state

b. Nuclear Importins in their mRNA bound state

c. Ran protein in its GTP bound state

d. Ran protein in its GDP bound state

c. Ran protein in its GTP bound state

The most rigid bond in a polypeptide backbone is the:

a. Bond between peptide Nitrogen and the Carbon containing side chain

b. Bond between peptide Carbon and the Carbon containing side chain

c. Peptide bond itself

d. All of them are equally rigid

c. Peptide bond itself

The major driving force that promotes tertiary folding of a polypeptide is:

a. Generated from GTP hydrolysis during its translation in the ribosome

b. Increase in entropy by minimizing the surface exposure of hydrophobic residues

c. Formation of covalent bonds between Cysteine residues

d. Formation of several non-covalent weak interactions between multiple residues

b. Increase in entropy by minimizing the surface exposure of hydrophobic residues

Secondary structures of a protein are determined by the:

a. Disulfide bonds between Cysteine residues

b. Rotational angles of N-Cα (Φ) and C-Cα (Ψ) bonds

c. Rotational angles of the N-C peptide bonds

d. Ribosomes that chaperone protein structure

b. Rotational angles of N-Cα (Φ) and C-Cα (Ψ) bonds

This type of Nucleoporins creates the permeability barrier of nuclear pores:

a. Central FG Nups

b. The Ran protein

c. Nuclear ring Nups

d. The Karyopherins

a. Central FG Nups

The main function of Signal Recognition Particle is:

a. Proteolytic cleavage of the signal peptide from a nascent polypeptide chain

b. Gated nuclear transport of a nascent polypeptide chain containing signal peptide

c. ER membrane translocation of a nascent polypeptide chain with signal peptide

d. Assembly of large and small subunits of the ribosome

c. ER membrane translocation of a nascent polypeptide chain with signal peptide

The BiP proteins play a critical role in:

a. Co-translational ER translocation of polypeptides

b. Post-translational nuclear transport of polypeptides

c. Post-translational ER translocation of polypeptides

d. Co-translational cytosolic translocation of polypeptides

c. Post-translational ER translocation of polypeptides

Rab proteins can recruit their respective effector proteins:

a. When bound and activated by Ran-GTPs

b. When linked with a GTP catalyzed by Rab-GEFs

c. When linked with a GDP catalyzed by Rab-GAPs

d. When bound and activated by Ran-GDPs

b. When linked with a GTP catalyzed by Rab-GEFs

The stop-transfer signals within a polypeptide chain causes:

a. Inhibition of signal peptide recognition by Signal Recognition Particle

b. Inhibition of signal peptide cleavage by the Signal Peptidase

c. Temporary pausing of protein translation by the ribosome

d. Release of transmembrane sequence into ER membrane

d. Release of transmembrane sequence into ER membrane

The major function of oligosaccharyl-transferase (OST) complex is:

a. Transfer of oligosaccharides from Dolichol to an ER lumen polypeptide

b. Glycosylation of Calnexin and promoting its function as an ER chaperone

c. Transfer of oligosaccharides from Dolichol to a cytosolic polypeptide

d. Attachment of glycosylphosphatidylinositol with an ER lumen polypeptide

a. Transfer of oligosaccharides from Dolichol to an ER lumen polypeptide

The major difference between COPI vs. COPII -dependent transport:

a. COPI = ER to Golgi, COPII = Golgi to ER

b. COPI = Cytoplasm to Nucleus, COPII = Nucleus to Cytoplasm

c. COPI = Cell surface to Early Endosome, COPII = Early Endosome to Cell Surface

d. COPI = Golgi to ER, COPII = ER to Golgi

d. COPI = Golgi to ER, COPII = ER to Golgi

Orientation of a transmembrane domain across ER membrane depends on:

a. The distribution of positive vs. negatively charged amino acids flanking it

b. The extent of N-linked glycosylation of amino acids adjacent to this region

c. The speed of protein translation by polyribosomes

d. The length of the nascent polypeptide chain

a. The distribution of positive vs. negatively charged amino acids flanking it

During vesicular trafficking, SM proteins are needed to:

a. Promote the nuclear trafficking of Nucleoporins

b. Promote efficient N-linked glycosylation of Syntaxins

c. Chaperone the folding and activation of Syntaxins

d. Dissolve the SNARE complex in ATP-dependent manner

c. Chaperone the folding and activation of Syntaxins

The main function of Multisubunit Tethering Complexes (MTCs) is to:

a. Promote polymerization of COPI, COPII, and Clathrin coats on vesicles

b. Recognize and dock a trafficking vesicle with correct organelle

c. Interact with and package a soluble cargo in correct vesicles

d. Modulate the lipid composition of organelles and vesicle membranes

b. Recognize and dock a trafficking vesicle with correct organelle

The “zero-layer” interaction of SNARE complex includes:

a. One Arginine from R-SNARE and three Glutamines from Q-SNARE

b. One Arginine from R-SNARE and one Glutamine of Synaptotagmin

c. Five Aspartate and Lysine residues at Synaptotagmin C2A domain

d. Three Arginines from Munc13 and one Glutamine from Munc18

a. One Arginine from R-SNARE and three Glutamines from Q-SNARE