Biol 102 Unit 3

Protein Transport

Proteins destined for secretion are synthesized _______ on rough endoplasmic reticulum (ER)-associated polyribosomes and then are moved _______ via vesicles.

co-translationally, post-translationally

Jamieson and Palade Pulse chase experiment

1) pulse with radioactive amino acids

2) chase with regualar amino acids

3) watch where the proteins go

To establish the path that secretory proteins take from their synthesis in the rough ER to their secretion outside the cell.

Ribosomal Subunits

a large subunit and a small subunit. These subunits come together during protein synthesis

Free Ribosomes

Ribosomes floating freely in the cytoplasm

Rough ER-associated Ribosomes

Ribosomes attached to the cytoplasmic surface of the rough ER. These ribosomes synthesize proteins destined for secretion

Common Pool

Both free and rough ER-associated ribosomes use the same pool of ribosomal subunits.

Proteins that are transported to the nucleus contain

Nuclear Localization sequence

Proteins destined for the nucleus are transported into the nucleus via the

Nuclear Pore Complex

LaminsProteins that binds to the nuclear localization sequence

Proteins that line the inner nuclear membrane to give structure to the nucleus

Import Receptors

Proteins that binds to the nuclear localization sequence

Proteins that binds to the nuclear import receptor in the nucleus

Ran - GTP

Nuleoporins

Proteins in the nuclear pore with FG-repeats

Sectory protein transport

1) MRNA recognizes the signal

2)MRna ceases translation

3)Signal regcognition partical attaches
4)signal recongisiton particle receptor attaches and postions protien at translocoon(hydrolysinig gtp)

5)Singla pepidase cleaves NLS and protein goes into the nucleaus

Where is the signal sequence

on the N-terminal of the poly peptide

Exocytosis

process by which cells transport substances from inside the cell to the outside by vesicles. Vesicles containing the material fuse with the plasma membrane, releasing their contents to the extracellular space.

Signal Recognition Particle

A protein-RNA complex that helps guide newly made proteins to the ER.

Signal Sequence:

A short peptide that directs a protein to the ER for further processing.

exocytic pathway steps

1) Proteins synthesis in the ER

2) Transport to the goli in er vesicle

3) tagged for destination

4) secreted

Signal Recognition Particle Receptor (SRPR)

A protein on the ER membrane that helps the SRP bring proteins to the ER.

Signal Peptidase:

An enzyme that removes the signal sequence from proteins once they are in the ER.

parts of the endomembrane system

Nuclear Envelope

Endoplasmic Reticulum

Golgi Apparatus

Lysosomes

Vesicles

Plasma Membrane

Steps of Cell Fractionation

1)Homogenization

2)Differential Centrifugation

• low-speed spin: Sediments nuclei and cell debris.

• Medium-speed spin: Sediments mitochondria, lysosomes, and peroxisomes.

• High-speed spin: Sediments microsomes (fragments of ER) and small vesicles.

• Very high-speed spin: Sediments ribosomes and macromolecules.