BIOB11H3 Chapter Notes - Chapter 12: Centromere, Disaccharide, Histone H2B

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turquoisejackal716

29 Apr 2011

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The nucleus contains chromosomes (condensed into chromatin = chromosomes + proteins), nucleoli, nucleoplasm, and nuclear matrix. The inner surface is bound by integral membrane proteins that are connected to filamentous meshwork called nuclear lamina (made up of lamins). A nuclear pore complex (npc) has an octagonal symmetry - contains only about 30 different proteins, called nucleoporins (at least 8 copies). Low-molecular-weight solutes may penetrate the nuclear pores by simple diffusion, whereas proteins and rnas have to pass throught he central channel with the help of special transport systems. The nuclear localization signal (nls) is a strech of positively charged amino acids in the c-terminus that enables proteins to pass through the nuclear pores. Mobile transport receptors include importins (move macromolecules from cytoplasm into nucleus) and exportins (opposite direction). Nls-containing cargo bind to a heterodimeric, soluble nls receptor called importin a/b in the cytoplasm.

Related Questions

2. Before nuclear pore complexes were well understood, it wasunclear whether nuclear proteins diffused passively into thenucleus and accumulated there by binding to residents of thenucleus such as chromosomes, or were actively transported andaccumulated regardless of their affinity for nuclearcomponents.
A classic experiment that addressed this problem used several formsof radioactive nucleoplasmin, which is a large pentameric proteininvolved in chromatin assembly. In this experiment, either theintact protein or the nucleoplasmin heads, tails, or heads with asingle tail were injected into the cytoplasm or into the nucleus offrog oocytes. All forms of nucleoplasmin, except heads, accumulatedin the nucleus when injected in the cytoplasm, and all forms wereretained in the nucleus when injected there.
A. What portion of the nucleoplasmin molecule is responsible forlocalization inthe nucleus?
B. How do these experiments distinguish between active transport,in which a nuclear localization signal triggers transport by thenuclear pore complex, and passive diffusion, in which a bindingsite for a nuclear component allows accumulation in thenucleus?

orangezebra695

1-Fill in the blank

Protein transport between the cytoplasm and the nucleoplasm requires a nuclear localization signal (NLS) at the C-terminus. The NLS binds to a/n ______ that binds it to a cytoplasmic filament of a nuclear pore.

2-Briefly summarize the four different levels of eukaryotic gene regulation

marooncicada200

1)A friend works in a biotechnology company and has discovered a drug that blocks the ability of ran the echange GDP for GTP. What is the most likely effect of this drug on nuclear transport?

a)nuclear transport receptors would be unable to bind cargo.

b)nuclear transport receptors would be unable to enter the nucleus

c)nuclear transport receptors would be unable to release their cargo in the nucleus

d)nuclear transport receptors would interact irreversibly with the nuclear pore fibrils

2)After isolating the rough endoplasmic reticulum the the rest of the cytoplasm, you purify the mRNAs attached to it. Which of the following proteins do you expect the mRNA from the rough endoplasmic reticulum to encode?

a) plasma membrane proteins

b)ER membrane proteins

c)Soluble secreted proteins

d)all of the above

3)For both actin and microtubule polymerization, nucleotide hydrolysis is important for?

a)stablilizing the filaments once they are formed

b)increasing the rate at which subunits are added to the filaments

c)promoting nucleation of filaments

d)decreasing the binding strenth between subunits on filaments

indigohare858

BIOB11H3 Chapter Notes - Chapter 12: Centromere, Disaccharide, Histone H2B

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