Cell Bio Chapter 10: Protein Trafficking through the Cytosol

This set of flashcards covers key concepts related to protein trafficking processes within a cell, emphasizing mechanisms and structural components involved in the transport of proteins to various destinations.

Protein Trafficking

Gets proteins to their final destination

Nucleus, cytosol, organelles, extracellular space

Proteins function everywhere in the cell and these places include

Signal Sequences

Short amino acid sequences written into the protein that direct the protein to its final destination.

On the N-terminus

Where is the signal sequence usually on

Hydrophobic amino acids

_____ targets proteins to rough ER

Positively charged amino acids

_____targets proteins to nucleus

Necessary

Without the signal sequence, a protein cannot get to its final destination

Sufficient

Nothing else but the signal sequence is required to get the protein to its final destination

Cytosol, nucleus, mitochondria, choroplasts

What are the cytosolic trafficking destinations?

Nuclear Pore Complex (NPC)

A large protein complex that allows proteins and other molecules to enter and exit the nucleus.

Cytoplasmic filaments

The cytosolic side of the NPC structure (latitudinal) has _____

Cytoplasmic ring, spoke ring, nucleoplasmic ring

The central channel of the NPC structure (latitudinal) is surrounded by a central ring that contains what 3 parts

Nuclear basket

The nucleoplasm side of the NPC structure (latitudinal) has _____

Small molecules, ions, small proteins

Nucleocytoplasmic transport diffuses only

Nuclear Localization Signal (NLS)

A signal that directs proteins to the nucleus, allowing their import through the Nuclear Pore Complex.

Cargo proteins binds to NLS (importin)

First step in nuclear import

Importin binds to cytoplasmic filaments and follows filaments into the nucleus

Second step in nuclear import

Importin/cargo protein binds to Ran-GTP and releases cargo protein

Third (last) step of nuclear import

Ran-GTP-importin crosses back to the cytosol

First step of nuclear import resetting

GTP-ase (GAP) activating protein binds to Ran, hydrolyzes GTP and Ran dissociates

Second step of nuclear import resetting

GDP-Ran returns back to the nucleus

Third step of nuclear import resetting

GEF replaces GDP with GTP

Fourth (last) step nuclear import resetting

Nuclear Export Signal (NES)

A signal that facilitates the export of proteins from the nucleus to the cytoplasm.

Ran-GTP binds to cargo protein-exportin complex in nucleus prior to export

Nuclear export is similar to import but what differences do we examine in their function? (First step)

In cytosol, GTP hydrolysis releases cargo protein

Nuclear export is similar to import but what differences do we examine in their function? (Second step)

Ran-GDP diffuses back to nucleus

Nuclear export is similar to import but what differences do we examine in their function? (Third last step)

Endosymbiosis

The evolutionary theory that explains how mitochondria and chloroplasts originated from free-living prokaryotes.

Plasma membrane folding

Nucleus, ER, and Golgi evolved from

Organelle-derived genes

Transcribed and translated in organelle

Nuclear-derived genes

Translated in cytosol and translocated across organelle membranes

Peroxisomes

Organelles involved in detoxification and lipid metabolism, containing enzymes for breaking down fatty acids. Found in all eukaryotic cells

Chaperones

At the start of translation (trafficking to mitochondria), what prevents the mitochondrial proteins from folding

Translocase of Outer Membrane (TOM)

A protein complex that facilitates the transport of mitochondrial proteins across the outer membrane.

Outer mitochondrial membrane proteins

Inserted into TOM and released into the membrane (second step of trafficking to mitochondria)

Translocase of Inner Membrane (TIM)

A protein complex that facilitates the transport of mitochondrial proteins across the inner membrane.

Matrix proteins

What proteins pass through TOM and TIM and fold in matrix

TIC and TOC

Similar to mitochondria the trafficking to chloroplasts use __ and ___ instead of TOM and TIM

Takes proteins to inter-membrane space

What does TOC do in trafficking to chloroplast

Takes proteins to stroma

What does TIC do in trafficking to chloroplasts