Describes intra-cellular trafficking of proteins, protein sorting, clinical aspects of protein targeting, and vesicle transport. Download and view in slide show mode for better viewing.

1. Intracellular Traffic
&
Sorting of Proteins
Ashikh Seethy
JuniorResident
Dept ofBiochemistry
MAMC– New Delhi

3. Ribosomes:

6. Overview:
• How proteins are targeted to their correct destinations?
• Clinical conditions associated with defects in protein targeting
• Drugs
• Mechanisms of certain toxins
• Maintenance of quality control in protein traffic
• Vesicle transport
• Degradation of proteins in proteasomes

7. A majorsorting decision is made earlyduring protein synthesis

8. Secretory pathway-mechanism

9. Gunter Blobel
• There is no difference between
structure of free and bound
ribosomes
• Selection of mRNA to the ER
membrane is not via direct
binding of the mRNA itself, but
rather via binding of its nascent
translation product
• Signal hypothesis

10. Signal peptide enables the binding of ‘bound ribosome’
-TheSignal Hypothesis
• N-terminal
• 13-36 residues
• 6-15 hydrophobic core flanked by hydrophilic
residues
• 1 or 2 basic residues near the N-terminal
• Small and neutral residues near the cleavage
site

11. Signal hypothesis:

12. Transmembraneproteinsareofdifferentclasses:
Signal
sequence

13. Type I Transmembrane Protein

14. Type II, III & IV Transmembrane Proteins

15. GPI linkedproteins

16. Someproteinsaretransportedpost-translationally

17. Quality Control in Endoplasmic Reticulum-ERAD

18. Clinical Significance

19. Unfolded Protein Response and DM

20. From ER to Golgi and Further

21. Vesicle transport

22. Coat proteins
Golgi>>>PM/Lysosomes ER>>>Golgi Golgi>>>ER

23. Fusion
• R or v-SNARE
 Synaptobrevin
• Q or t-SNARE
 Syntaxin
 SNAP-25 [Synaptosome
Associated Protein]
• Disassembly:
SNARE
SNAP
NSF

24. Fusion

25. Vesicletransport

26. ER resident proteins havea KDEL sequence
• C-terminal:
 KDEL
 KKXX
 KXKXXX
• "If found, please return
to ER"

27. Targeting tolysosomes

28. I-cell disease
• Mucolipidosis II
• UDP-N -acetyl glucosamine
phosphotransferase
• Cultured fibroblasts-deficient in numerous
lysosomal enzymes
• Inclusions in lysosome
• These enzymes were found to be present
in excess in tissue culture media and in
extracellular fluids
• Psychomotor and skeletal defects

29. Cytosolicpathway

30. Proteinimport to peroxisomes:
• Peroxisomal matrix
targeting
sequences
• PTS-1:
 SKL
• PTS-2:
 N-terminal
(R/K)(L/V/I)X5(H/Q)
(L/A)

31. The Zellweger spectrum:
• Zellweger cerebrohepatorenal syndrome
• Neonatal adrenoleukodystrophy
• Infantile Refsum disease
• Peroxisomal biogenesis disorders
• Mutation in PEX genes
 Impaired plasmalogen synthesis
 Impaired very long chain fatty acid (VLCFA) beta oxidation
 Impaired alpha oxidation

32. Signal sequences for nuclear import are not cleaved
• Nuclear Localisation Signal
– Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val

33. Proteintargetingto mitochondria

34. Protein degradation
• 76 residues
• Highly conserved
• Isopeptide bonds
 Juvenile onset Parkinsonism
 HPV
• 26 S proteasome
 20S core subunit
 19S regulatory subunit
• Bortezomib and Carfilzomib

35. Summary

36. Than
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