Intracellular Transport Lecture Notes

Flashcards about intracellular transport, protein sorting, and mechanisms of protein transport into organelles.

What are the three organelles that are heavily discussed in the context of intracellular transport?

Endoplasmic reticulum, the Golgi apparatus, and the plasma membrane.

What term is used to describe how proteins are distributed into one place or another within a cell?

Protein Sorting

How many strategies are there for intracellular protein distribution, according to the lecture?

There are three strategies for how proteins get distributed into different organelles.

The speaker mentions that when the mechanisms of protein localization don't function correctly, it could lead to what?

Mislocalization of proteins, caused by disruptions in protein sorting

What surrounds eukaryotic cell organelles, allowing control over the passage of molecules?

Membranes

What terms are used to describe the movement of molecules into and out of organelles?

Import and export.

What is the definition of protein sorting, as described in the lecture?

Proteins are distributed to specific organelles or between organelles, involving import and export.

What is a signal sequence in the context of protein sorting?

A special sequence within a protein that is essential for directing it to a specific organelle.

A signal sequence to bring something into an organelle is also known as what?

Import sequence

What is the typical length range of a signal sequence in a protein?

The sequence can vary from approximately three amino acids to about 60, depending on the signal sequence and its destination.

What's a vesicle made of?

Little bubble of phospholipid

What term is used for transporting things from one place to another via vesicles?

Vesicular transport.

What motor proteins are responsible for vesicular transport from one organelle to another?

Kinesin and Dynein.

What organelles utilize vesicles significantly for protein transport?

ER to Golgi and Golgi to the plasma membrane

What do proteins need to be able to be imported via pores, translocators, or vesicles?

Signal sequences.

What complex is associated with pores in the nucleus?

Nuclear Pore Complex (NPC)

Which organelles extensively use translocators to transport proteins?

Mitochondria, chloroplasts, and the endoplasmic reticulum.

Approximately what is the typical number of amino acids in a signal sequence?

The range is approximately 15 to 60 amino acids.

What is the specific name of the signal sequence that allows proteins to enter the nucleus?

Nuclear localization signals (NLS)

What is the term for shuttling proteins in and out of the nucleus?

Cargo shuttling

What do you call the double membrane surrounding the nucleus?

Nuclear envelope

What are the proteins that make up the nuclear pore complex (NPC) called?

Nucleoporins

What are the structures which initially tether proteins at the nuclear pore?

Cytosolic fibrils

What protein recognizes and binds to the NLS (nuclear localization signal) on a protein destined for the nucleus?

Nuclear import receptor (NIR)

What is the nuclear import receptor important for?

Import proteins into the nucleus.

What happens when the protein and nuclear import receptor reach the inside of the nucleus?

It disassociates, with the nuclear pore receptor letting go of the protein of interest.

What molecule is essential for helping the nuclear import receptor and protein cross the pore into the nucleus?

Ran-GDP

What happens to Ran-GDP upon entering the nucleus?

It is converted to Ran-GTP

Which protein in the nucleus causes Ran-GDP to become Ran-GTP?

Ran-GEF

What molecule promotes the hydrolysis of Ran-GTP back to Ran-GDP outside the nucleus?

Ran-GAP

A mitochondrial protein wanting to enter the mitochondria must have what?

Mitochondrial import sequence

Name the two parts of the protein import machinery that act like a mouth that picks up particular proteins

Mitochondrial import receptor and a mitochondrial translocator

What must happen to a protein before it can pass through the translocator into the mitochondria?

It unfolds before crossing the translocator.

After entry via the translocator, where does the unfolded protein then reside?

Mitochondrial matrix

Which proteins facilitate refolding once a protein is inside the mitochondrial matrix?

Chaperones

What enzyme removes the mitochondrial import sequence?

Signal peptidase

What is the space on the inside of the endoplasmic reticulum called?

ER lumen

The presence of what on the ER membrane makes it what kind of ER?

Rough ER, due to ribosomes

If a protein is destined to be imported in the ER, what sequence must it have once it is made?

Endoplasmic reticulum (ER) signal sequence.

What protein recognizes the ER signal sequence as it is being made?

Signal recognition particle, SRP

After the SPR grabs the protein of interest, what does it then do?

Brings the ribosome with the protein to the SRP receptor.

After the SRP receptor and SPR form a complex, what then happens?

The SRP disassociates, and the protein starts going across the translocator.

What sequence is used to stop the process of protein transfer into the ER, so that the protein can stay in the ER membrane?

A start-stop transfer sequence.