Lecture 17 : Moving into the nucleus Flashcards
What does compartmentalisation allow
- Separates organelles
- Vesicle transportation
- Provides distinct environments (lysosomes have low pH)
- Protects microenvironment from toxic metabolites
What are the 3 mechanisms of transport between molecules
Gated transport - pores
Transmembrane transport - direct passage across intact membranes
Vesicular transport - Fusion of membranes
Function of nucleus
Communicates with rest of cell, allows gene expression to occur, separates genetic material from rest of cell
Structure of nucleus
- nucleolus is not membrane bound
- Outer membrane continuous with ER
- Inner membrane has pores
What is nuclear lamina
- Nuclear scaffold
- Maintains structural integrity
- Made from filaments and proteins
- Important in gene regulation, cell division, DNA replication, nuclear pore complexes (35nm wide), a molecular sieve
Nuclear pore complex structure
One of the biggest protein complexes in mammalian cell
What can be transported through the NPC?
- By passive diffusion
- Proteins
- mRNA
- tRNA
- Viruses
- Ribosomal subunits
- IMPORT AND EXPORT OF PROTEINS ACROSS NPC IS REGULATED BY INTERACTIONS BETWEEN PROTEIN CARGO AND NUCLEAR TRANSPORT RECEPTORS AND SMALL GTPases
How are proteins imported and exported across the nuclear membrane (3 steps)
- Cargo recognised and bound by nuclear transport receptors
- NTR-cargo docks on the NPC by GF Nups and cargo is translocated through NPC
- NTR-cargo dissociated
Miossing shit
Movement through pore
How is directionality contrrolled
Phosphorylation of cargo
SAkip[ped a lot
What is required for export of proteins to cytoplasm?
- Exportins (crm1 and nxf1)
- Require Ran-GTP for interaction with cargo
- Export of mRNA does NOT require RanGTP gradient
