Chap. 8 part 2 Flashcards
role of the golgi body (Golgi complex)
Cis Golgi Network - Functions to sort proteins the ER or the next Golgi station
Medial cisternae - where processing take place
Trans Golgi Network - functions in sorting proteins either to the membrane or various intracelluar destinations
Functions of glycosylation
the N-linked oligossaccharide that was added to nearly every protein in the ER is further process int he Golgi apparatus
Gives a cell the ability to generate many chemically distinct molecules at the cell surface
basic difference between vesicular transport and the cisternal maturation model
describe each model
Vesicular Transport Model
- cargo is shuttled through the cis to the trans Golgi network
Cisternal Maturation Model
- the vesicular tubular cluster matures into a cistern and moves along from the cis to the trans face
There is retrograde transport of vesicles in both models
What is the VTC and where is it located?
it is the Vesicular Tubular Cluster and its located in the endoplasmic reticulum-golgi intermediate compartment
- it mediates traffic between the golgi and ER
basic structure and role of COP1
Protein Coated vesicles that move materials backwards (retrograde transport) from the VTC in the ERGIC to the ER
basic structure and role of COP2
Protein Coated vesicles that move materials forward (antegrade transport) to the VTC in the ERGIC from the ER
role of clathrin coated vesicles
to move materials from the trans golgi network to endosomes and lysosomes
Role of a KDEL sequence
This is the signal on the resident ER proteins that get transported to the golgi in COP2 vesicles to get them returned by to the ER by COP1 vesicles.
- if they don’t have this sequence, they will never return back
- the sequence binds to a KDEL receptor
How does vesicle budding begin?
- a recruitment of GTP binding protein to the donor membrane
- binding of the cytosolic coat protein to the domain of the membrane cargo proteins
Role of V SNARE and example
they mediate membrane fusion, they become incorporated in the membrane of the vesicles during budding
example: synaptobrevin
role of T SNARE and example
they mediate membrane fusion, they are in the target membrane during budding
example: syntaxin
Role of a mannose 6-phosphate tag
to get the lysosomal enzymes to the trans golgi
the TAG gets added in the cis golgi
Role of a mannose 6-phosphate receptor
to detect the tag and get the lysosomal enzymes from the TGN to lysosomes
Role of lysosome
they contain 50 types of hydrolytic enzymes (produced in the RER) virtually hydrolyze every type of macromolecule.
Optimal pH is 4.6
How are hydrolytic enzymes targeted?
They get tagged with phosphorylated mannose residues and recognized by MPRs (mannose 6-phosphate receptor)
what is bulk phase endocytosis?
aka Pinocytosis
its the non specific uptake of extracellular fluids
what is the receptor mediated endocytosis?
or clathrin mediated endocytosis
bring the uptake of specific ligands to their receptor on the external surface of the plasma membrane
The formation of clatherin coated vesicles
the outer shell is made of clatherin and triskelion which consist of three large and three small polypeptide chains
the inner shell is made of GGA adaptor proteins which interacts with the clathrin, MPR and G proteins
Role of GGA Adaptor proteins
contain multiple subunits having different functions
- they engage the cytoplasmic tails of specific receptors to select bound cargo molecules and bind and recruit the clatherin molecules of the overlying lattice
Role of dynamin
its a G protein needed to release clathrin-coated vesicle from the membrane where it forms
- it pinches off the vescicles from the exoplasmic face with the help of GTP
Basic Mechanisms of Phagocytosis
reuptake of large particles and is receptor mediated in mammals
4 compartments of mitochondria for protein
- matrix
- inner mitochondrial membrane (IMM)
- intermembrane space
- outer mitochondrial membrane (OMM)
Basics of mitochondrial import
1) the protein has to be relatively unfolded or extended
2) Has to go through TOM
3) rather go through TIM22 or TIM23
Role of TOM complex
Transporter of outermsmbrane which has an receptor on its channel
Role of TIMs complexes
Transporter of inner membrane
TIM22: for integral proteins of the inner mitochondrial membrane
TIM23: for protein for the matrix
Both have receptors
Role of location of signal sequences
for TIM22 the signal sequence is internal and remain a part of the molecule
for TIM23 the signal sequence is at the N terminus and it’s removed
what is the structure of the nuclear envelope
it has 2 membranes and the outer one is continuous with the ER
role of nuclear pores (nuclear pore complex)
allows ions, small metabolites and globular proteins to go through
ex. nuclear protein synthesized in the cytoplasm, mRNA, tRNA ribosomal subunits
Nuclear Localization Signals
there is a specific stretch of positively charged amnio acids that allows access into the nucleus, if there is an mutation, the protein fails to localize into the cell.
if a NLS is fused on a non protein, that will become concentrated in the nucleus
How does a protein get imported into the nucleus?
1) the importin alpha/beta cargo complex docks on the cytoplasmic filament before it moves into the nucleoplasm through the nuclear pore complex
2) in the Nucleoplasm, importing Beta interacts with Ran-GTP to release the cargo
3) They both relocate into the cytoplasm and Ran-GTP is hydrolyzed into Ran-GDP
4) importin alpha is brought into the cytoplasm by exportin
5) importin Beta can now bind to importin alpha
cycle restarts
what kind of protein Ran is
its a member of a class of protiens called small-GTPases
How does Ran-GTP turn into Ran-GDP?
Ran-GAP and Ran-GEF help with the enzymatic hydrolysis to REPLACE the RAN-GtP with RAN-GDP
What is RAN-GAP
GAP are GTPase Activating Proteins
What is RAN GEF
GEF is Guanine Nucleotide Exchange Factor
