The Nucleus: Structure, Nuclear Transport (5) Flashcards
nucleus
storage & decoding of genetic info
nuclear matrix
PRO containing fibrillary network
where DNA is attached & anchored to the nucleus
Nucleolus
granular region, rRNA synthesis & ribosome assembly
Nuclear envelope is continuous with ___
endoplasmic reticulum
nuclear envelope
2 lipid bilayer membranes
membrane - lumen sac - membrane
nuclear lamina
denser layer of intermediate filaments within the inner membrane
composed of lamin PRO
provides structure to the nucleus & is the heterochromatin binding site
What part of the nuclear membrane needs to be broken down in mitosis?
nuclear lamina
What is the nuclear pore complex composed of?
nucleoporin PROs & cytoplasmic filaments extending into the cytoplasm
What is the role of cystolic fibrils?
restrict the entrance of large molecules
How do nuclear pores regualte the traffic in & out of the nucleus?
Nuclear localization signal NLS
What is an NLS?
positively charged AA sequence added to PRO providing the PRO with access into the nucleus
Experiment: What happens when they altered the NLS? & what AA was replaced?
PRO no longer accumulated in the nucleus, accumulated in the cytoplasm
replaced a Lys with Thr (a nonpositively charged AA)
Experiment: How did using recombinant DNA techniques with the NLS work? & what did this provide evidence of?
attached NLS to a PRO that normally doesn’t contain NLS, enabling the PRO to enter the nucleus
proved that there are nuclear transport receptors
Importins
recognize NLS & bring PROs in
Exportins
recognize NES & bring PRO out
diffusion
movement of molecules from a region of high concentration to a region of low concentration
What are the steps in the mechanism of PRO import through the nuclear PRO complex?
- NLS attaches to alpha
- Beta attaches to cytoplasmic filament
- Move into nucleoplasm (no E consumed)
- RanGTP attaches to complex, causing the complex to dissociate beta & RanGTP remain bonded, alpha leaves
- RanGTP & beta move back to cytoplasm (diffusion)
- Exportin binds to alpha back to nucleus & RanGTP –> RanGDP+phosphate causing beta to be released (Hydrolysis E consuming)
- Exportin brings alpha into the cytoplasm & RanGDP diffuses back to nucleoplasm
- RanGDP RanGTP via RCC1 & alpha beta complex reforms
RCC1 never ____
goes out of the nucleus
RANGAP never ___
goes into the nucleus
is GDP –> GTP an energy consuming or producing step?
consuming
is GTP –> GDP an energy consuming or producing step?
producing
What controls the mechanism of PRO import through the nuclear PRO complex?
GTP to GDP conversion
causing a steep gradient of Ran-GTP across the nuclear membrane
Role of RanGAP
maintains low concentration of Ran-GTP in cytoplasm
role of RCC1
maintains high concentration of Ran-GTP
