Sorting, the RER, and the Golgi Flashcards
Signal peptides
N-terminal extensions composed of 5-30 basic/hydrophobic AA
Signal patches
Distant parts of protein sequence brought together upon folding
Types of translocation
Post-translationally (C)
Co-translationally (N)
Post-translational translocation characteristics
SOluble and posses patch or signal peptide
Sorting into the nucleus
Uses NLS (short, basic squences on N-terminus of proteins) Importin comes in with protein, uses Ran-GTP to get out
Sorting into mitochondria process
Precursors protein with MTS…binds receptor…moves to protein translocator…pulled into protein and signal sequence cleaved by peptidase
Sorting into mitochondrial membrane
Matrix targeting sequence binds TOM protein of outer…pulls through into TIM…TIM recognizes the intermembrane space-targeting sequence and diffuses over to protease…protease will cleave the matrix targeting sequence and the intermembrane space targeting seqence stays in inner membrane
Intermembrane space sorting
Intermembrane space targeting sequences pass through Tom receptor
Outer membrane mitochondrial proteins sorting
Hydrophobic transmembrane signal…recognized by TOM, passed to SAM, mim and mdm act and released into membrane
Peroxisomes sorting process
C-terminal and N-terminal ends…peroxisomal targeting sequence binds pex5 receptor…receptor binds pex14 receptor on membrane…moves through via pex 10 and 12
Co-translational translocation
Used for proteins that are secreted, membrane bound, resident in ER, golgi, or lysosomes
Signal for co-translational translocation
N-terminal signal of hydrophobic residues
Process of co-translational location
SRP binds to N terminal signal sequence…SRP binds to SRP receptor on ER membrane surface associated with translocon…GTPase activity of both SRP and SRP receptor results in opening of the translocon…signal peptidase claves the signal sequence
What is attached into the ER
N-linked glycosylation
Linked to asparagine - X - serine/threonine
What is in the ER membrane that holds the glycosylation chain?
Dolichol
Glucosidase
Chews the oligosaccharide attached to the protein
ERAD system
Sends misfolded proteins for degradation
Glycosylated proteins that pass ERAD
Encapsulated in transition vesicles and transported via anterograde transporrt
Surface of vesicles from ER t oGOlgi coated with
COP2
Modifications in Golgi
O-linked oligo added to serines and threonines
Mannose-6-P added to proteins goign to lysosomes
Cis golgi network
Phosphorylation of oligosaccharides on lysosomal
Cis cisterna
Removal of Man
Medial cisterna
Removal of man and addition of GlcNAc
Trans cisterna
Additon of Gal
Trans GOlgi netowkr
Addition of NANA (common sialic acid)
And sortint
Glycosylation purposes
Sorting
Stabilization of secreted proteins and transmembrane with extracellular domains
Biomolecule recognition
Golgi to lysosomes
Binds to M6P receptor…travels in vesicle with clathrin coat to the early endosome…M6P dissociated…Endosome fuses to lysosome
Receptor recycled
Secretory vs. transport vesicles
Secretory - regulated exocytosis
Transport - constitutive exocytosis
