Topic 13: intracellular Compartments and Transports
Endomembrane system: inlcude
endoplasmic reticulum (ER)
Golgi apparatus
lysosomes
endosomes
vacuoles
any kind of membrane structures
important bc
endomembrane system help transport things w/in the cell
often time see different organelles in eukaryotic cells are membrane bound organelles, when they need to transport materials like proteins they always go through those structures
theres a donor compartment budding
to form a vesicle; vesicle keep moving bc vesicles are also membrane bound structure inside of cell
then the fuse with the reception to transport
secrete out of cell through this process
Several Distinct pathways
secreting (biosynthetic) pathway
Constitutive secretory pathways
Endocytic pathway
receiving form the outside
certain type of hormones
ligand cells will synthesis those hormones constitutively
Regulated secretory pathways
like w/ hormone insulin
the hormone insulin secretion is responding to the blood sugar level
many things are regulated secreation
making certain type of hormones ; but this is less common
The Traffic across Plasma membrane
approach to study of cytomembrane
insight gained from biochemical analysis of subcellular fraction; cell homogenization & organelle isolation
post-chase experiment
study how proteins are synthesized inside of cell; so radioisotope (S35) was used to label protein; helps cells to grow
called pause and chase; to observe where the protein are located
protein synthesis are started up by the ribosomes
SD35 are attached in the ER
Green Fluorescent protein (GFP)
from jelly fish and placed into Ecoli, cDNA to was used to express
able to do pause and chase experiment; they would ligate it to the target protein and the GFP could be seen moving through the cell
Protein traffic
protein can be synthesized by the ribosomes located in the cytoplasm but proteins later on go into the nucleus
Helices, DNA polymerase, TF, RNA polymerase
Transport through nuclear pores
transports across membrane
transport by vesicle
Proteins need to be transported to the ER
Endoplasmic Reticulum (ER)
Endoplasmic Reticulum
rough ER
smooth ER
GFP showed the direction of the protein
tubular, curves through cytoplasm ; no associated ribosomes
much more ribosomes attached; good insulates; like pancreas
lots of protein synthesis
ER-Golgi plasma membrane traffic
signal hypothesis pathway
places synthesis is determined by information in particular protein, specially by the n-terminal part of the protein
SIGNAL SEQUENCES (6-15, very hydrophobic) , this determines proteins information
ER signal sequence is the first identified signal sequence inside of cell
Synthesize by ribosomes attached to the ER
Important bc they are magnesium’s inside the cell to recognize the ER signal sequence & to bring the whole complexes to the ER
will be reconized by SRP to bring the whole complex to the ER
translocation channel will serve like a doc for those SRP bring those whole complex
(SRP) signal recognizing proteins ; made from 6 different proteins but also small RNA molecule
SRP receptor, receives the SRP
Translocation channel; this protein is used to get inside the lumen of the ER
in the lumen the enzyme SIGNAL PEPTIDASE; this will cut off the signal sequence ! so they wont be present in the mature protein
so signal sequence in the mature protein
bc if its not cut off, when it budds off the protein will be recognized by the SRP again and brought back and never make it to golgie complex to get secreted
the proteins need to be embedded in the cell plasma membrane called INTEGRAL PROTEIN SYNTHESIS
need IPS to stay in the plasma membrane
they also have hydrophobic stop-transfer sequence and stops the protein from getting inside of the ER
The Golgi apparatus
The main purpose is to add sugar groups to the proteins
called glycosylation
vesicles are very important bc they move a lot
The nuclear traffic
complex structure
nuclear lamina thin filamentous meshwork
Mutation may cause very bad diseases
nuclear pore complex guides what can go in
nuclear localization signals (NLS) short, with a lot of argine and enzime and get recognized and allowed to get in
need energy consumption; uses GTP
Mitochondria
they are mitochondria sequence and lets them in to get inside
adaptin will attach to the receptors recruiting catherine ( protein will help bud off the whole complex