Protein Sorting for Nuclear Transport Flashcards
What Organelles are NOT a part of the Endomembrane System
The Mitochondria and Chloroplast
Signal Sequences
Direct the protein to the appropriate cellular location
- these sequences are a part of the polypeptide chain when it is made.
2 structures of Unfolded Proteins
1:The signal sequence is found on the end terminus.
2: Multiple signal sequences can also be found in different areas throughout the peptide chain at multiple locations
Structure of the Nucleus
-Double Bilayer Nuclear Membrane
-Outer Membrane is continuous with the endoplasmic reticulum
-Genome must be protected from molecules trying to enter/exit the nucleus-> Nuclear Pore Complex
Nuclear Pore Complex
The gatekeeping mechanism within the nucleus which is one of the largest and most complex protein structure in a Eukaryotic Cell
What is the Importance of the Nuclear Pore?
-Gate for entry and exit for proteins
-Small eater-soluble molecules can pass freely
-Meshwork of Nucleoporin proteins which create the structure and fill the center channel
-Larger proteins require assistance
What do proteins bind to FIRST when they are getting imported into the Nucleus?
Cytosolic Fibrils
This structure extends into the nucleus and contains the cytosolic fibrils within the nuclear pore. This structure makes non-covalent interactions with the imported proteins
Nuclear Basket
These types of molecules and flow through the nucleus freely
small water-soluble molecules
These types of molecules need to be regulated before entering the nucleus
Larger monomer macromolecules
Proteins that are destined to be transported to the Nucleus require:
NLS: Nuclear localization signals- forms a signal patch on a polypeptide to signal the protein needs to be transported to the nucleus.
-this signal is composed of exposed lysines and or arginines. This amino acids are positively charged
Where is the signal sequence found for proteins being transported to the nucleus?
Nucleus polypeptides can have multiple signal sequences throughout the protein.
-proteins transported to the nucleus are in there fully folded form
Proteins that are transported to the nucleus pass the nuclear pore by ____ ______.
Active Transport- this process requires energy
3D nuclear proteins must bind to a specific protein to enter the nuclear pore
3-D proteins with the NLS sequence must bind to the Importin protein for transport into the nucleus
- when the proteins bind to Importin is cases of a conformational change which will expose new non-covalent binding sites.
- the non-covalent binding sites then bind to cytosolic fibrils. this sequential binding will slowly move the complex into the nucleus
After Importin and the bonded Protein enter the cell, what binds to Importin to release the protein cargo?
RAN-GTP
