Protein sorting Flashcards
Protein regulation
regulation of the amount of any one protein in the cells controlled at the level of transcription and translation
Ubiquitin
a marker in eukaryotic cells that target cystosolic and nuclear proteins for rapid proteolysis
Proteasomes
large, multi-subunit protease complexex that recognize and degrade polyubiquinated proteins.
molecular chaperone
proteins that facilitate the folding and translocation of other proteins. keeps protein unfolded until completely synthesized
faulty chaperone protein
mad cow disease
Free ribosomes
although the synthesis of ALL proteins start on free ribosomes, some continue to be synthesized on free ribosomes, while others finish up translation on these free ribosomes as they become membrane bound
branches of protein sorting
cystolic (free)
secretory (free and membrane bound proteins)
Targets of cystolic pathway
nucleus, peroxisomes, mitochondria, chloroplasts
Targets of secretory pathway
Plasma membrane, secretory vesicles, endosomes, lysosomes, extracellular space, ER and Goldi associated proteins, nuclear membrane proteins
what decides where protein goes
protein
Rough ER
involved in protein metabolism, entry point for most proteins into the secretory pathway
Co-translational proteins
translocation of proteins into ER during their synthesis on membrane-bound ribosomes
Signal sequence
signal for ribosome attachment to the RER at N terminus, hydrophobic
Signal recognition particles, or SRPs
that recognize and bind to signal sequences, while protin is being translated
Signal recognition particle receptors
proteins on membrane of the the ER that bind the SRP
translocon
membrane channel composed of secretory proteins through with a signal sequence are transported into the ER
BiP
molecular chaperone in ER
Signal Peptidase
recognizes signal sequence and cleaves it off growing polypeptide chain
GTP binding
triggers the transfer of signal sequence into translocon
GTP hydrolysis to GDP
dissociation of SRP from SRP receptor and ribosome-mRNA complex
Major protein in Secretroy pathway targeted to the RER
Proteins destined for secretion
Intergral membrane proteins
Stop Transfer sequence
Alpha Helix, stops the polypeptide from entering the lumen of the ER and changes the conformation of the translocon channel so membrane opens, releasing the polypeptide chain to the ER membrane
Trans and Cis face of Golgi
Cis is closest to ER where proteins enter, while trans is furthest from ER, where proteins exit
Vesicle protein coats
Clathrin, COPI, COPII
plays key role in ensuring vesicles reach correct targets
Lysosomes
membrane closed organelles that contain an array of enzymes capable of breaking down all types of biological polymers at acidic pH
mannose 6 phosphate receptor
binds only mannose 6 phosphate which should be only bound to lysosomal proteins
snare hypothesis
fusing of different membrane of vesicle is energy dependent
Nuclear pore compexes
establishes nuclear composition as unique form the cytoplasm. gene assembly, RNA processing and ribosome assembly
Laminin
Nuclear lamina protein
Nucleoporins
pore proteins
Nuclear localization signals
specific amino acid sequences that are recognized by transport receptors and direct protein transport from cytoplasm into nucleaus through nuclear pore complex
Karyopherins
family of transport receptors
Importins
karypherins that direct nuclear import
Ran
regulates imprtin cargo complex movement. GTP binding protein
Nuclear export signals
specific amino acid sequences that target proteins for export out of nucleus
Exportins
members of karyopherin family, similar mechanism to importin
