lect 21: regulated protein turnover
DESCRIPTION
LECT 21: REGULATED PROTEIN TURNOVER. Cellular proteins have different stabilities. It is the combination of synthesis and degradation rates that determines the level of a protein in a cell, and changes in either rate can serve as means to regulate - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/1.jpg)
LECT 21: REGULATED PROTEIN TURNOVER
Cellular proteins have different stabilities. It is the combination of synthesis and degradation rates that determines the level of a protein in a cell, and changes in either rate can serve as means to regulate a protein’s concentration in the cell.
Protein degradation in response to extracellular signals is an important component of some intracellular signaling pathways.
Protein degradation is further required to mis-folded or de-folded proteins, which would otherwise be capable of forming insoluble aggregates.
![Page 2: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/2.jpg)
![Page 3: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/3.jpg)
Machinery for Protein Degradation Within Cells
Cytosolic proteins targeted for degradation are digested in the 26S proteasome, a large multienzymatic structure.
Membrane proteins targeted for degradation travel through endosomes to the lysosome, whose lumen contains a collection of proteases.
Both targeting processes employ the covalent tagging of proteins with ubiquitin, a small 76 amino acid polypeptide.
![Page 4: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/4.jpg)
![Page 5: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/5.jpg)
![Page 6: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/6.jpg)
![Page 7: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/7.jpg)
![Page 8: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/8.jpg)
![Page 9: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/9.jpg)
EGF
EGFR(inactive)
EGFR(dimerized, phospho-Y)
active
EGF
POSITIVE SIGNALING SIGNAL TERMINATION
Cbl (E3)
Several pathwaysactivated for growth
or differentiation
Internalization,ubiquitination,
trafficking to lysosome
Cbl Terminates Growth Factor Signaling Thru Receptor Ubiquination
![Page 10: LECT 21: REGULATED PROTEIN TURNOVER](https://reader036.vdocument.in/reader036/viewer/2022062500/56815a83550346895dc7f1d9/html5/thumbnails/10.jpg)
Proteasomal Degradation Can Activate Signaling Pathways:Transcription Via NFB
UbUbUbUbUbUb
UbUbUbUbUbUb
Nuclear TransportDNA Binding
Transcription Activation
ProteasomeDegradation
NFB
IB
ExtracellularSignal
IKK E3