1.12: Intracellular Vesicular Transport Pt 2 Flashcards
which face of the golgi is the er closer to
the cis face
name the cisternae in order from cis to trans face
cis, medial, trans
when cargo goes from the er to the cis golgi, the adaptor proteins of the inner copII coats binds to proteins with what feature
those with exit signals
are all exit signals the same
no
when cargo wants to go from er to cgn, what coat is used on the vesicles
copII coated
soluble proteins are bound by ____________, transmembrane proteins are bound by __________
soluble proteins are bound by cargo receptors, transmembrane proteins are bound by copII coat
when cargo has no exit signal, how do they get packaged
due to high concentration in the er they left through diffusion
when do copII coated vesicles shed their coat
after they bud from the er exit site
what is it called when vesicles fuse together
vesicular tubular clusters
where do vesicular tubular clusters go to
golgi
what molecules are needed to untangle the v and t snares
nsf and atp
what type of coat does retrieval/retrograde transport involve
copI coated vesicles
for retrieval/retrograde transport, what do the vesicles contain
escaped er resident proteins, proteins involved in vesicle budding from er
where can retrieval/retrograde transport come from
vesicular tubular clusters, golgi
er resident proteins have which signals
er retrieval signals
soluble er proteins have which retrieval signal and are bound by which receptor
KDEL, KDEL receptor
soluble er proteins with the KDEL retrieval signal are packaged into what type of vesicles
copI - coated transport vesicles
the er retrieval signals are bound by what
copI coats
what is kdel receptor binding affinity regulated by
pH
at what condition is kdel receptor-kdel binding affinity high and where is it high
binds in acidic pH, at vesicular tubular clusters and golgi the receptors have high affinity for kdel
at what condition is kdel receptor-kdel binding affinity low and where is it low
kdel is released in neutral ph, and at ER there is a low affinity for kdel
how is pH regulated in the lumens of organelles
v-type ATPase, H pump
where on the signals are the receptors
which part of the protein are the signals attached to
on the c terminus
do all er and golgi resident proteins have retrieval signals
no
how do proteins end up in the correct compartment if they don’t have retrieval signals (2)
- different transport rates: eg some golgi enzymes cycle between the er and golgi, but transport to the er at a slower rate (tends to bind better for proteins going a certain way)
- proteins retained in resident compartment: proteins that function in the same compartment form large complexes which prevents packaging into transport vesicles
what proteins keep transport vesicles and golgi cisternae close
tethering proteins
processing of n-linked oligosaccharides occurs where
golgi
describe the vesicular transport model through the golgi cisternae
from cis to trans: copI coated transport vesicles with cargo move forward from one golgi cisterna to the next
retrograde transport: copI vesicles return escaped resident ER proteins and golgi enzymes
which transport model of moving proteins through the golgi cisternae is faster
vesicular transport model
describe the cisternal maturation model
everyone get promoted: cisternae move through the golgi apparatus, vesicular tubular clusters from the er fuse to become the cgn (cis golgi network), each cisterna becomes the next, existing trans cisterna moves to the TGN
retrograde transport by copI vesicles move golgi enzymes and er resident proteins back
what factor is common between both methods of protein transport within the golgi
both have the same pathway for retrograde transport
what is the tgn
trans golgi network: complex network of membranes and vesicles that is a major branch point where proteins are sorted into different vesicles
vesicles from tgn are transported where and what is the cargo
transported to late endosomes (late endosomes gradually mature into lysosomes) and they carry lysosomal hydrolases
name the purpose of lysosomal hydrolases
needed for lysosome function and degradation of macromolecules
where are acid hydrolases synthesized and processed
synthesized in the er and processed in the golgi
what do acid hydrolases do and list some examples
degrade macromolecules
examples: nucleases, proteases, glycosidases, lipases, phosphatases, sulfatases, phospholipases
how does the cell ensure its safety from the acid hydrolases
- it’s only active at acidic pH
- there is a membrane around the lysosome/endosome
describe M6P (mannose-6-phosphate) regarding being a signal for vesicular transport of lysosomal hydrolases to the lysosome/endosome
from the er, there is a lysosomal hydrolase precursor w mannose. there is an additional of phoso-N-acetyl glucosamine (n linked oligosaccharide added in er), the m6p signal is uncovered by loss of N-acetyl-glucosamine == mannose residue phosphorylated thus it becomes m6p in the cgn. then it goes to tgn, m6p receptors here package lysosomal hydrolases, lysosomal hydrolases are released in the late endosome through dissociation at acidic pH and the m6p receptor goes back in retrieval pathway (optional step is the removal of phosphate when it reaches the endosome)
