I have tried to make a precise presentation on protein transport, targeting and sorting into organelle's other than nucleus. Hope this might help you. Comments are welcome.

1. CELL BIOLOGY
PHD COURSE WORK.
P R E S E N T E D B Y
JAHIR AHMED
Protein Transport, Targeting
and Sorting.

7. 10-9
Folding in the Endoplasmic
reticulum

9. COP 2 TRANSPORT VESICLE.

10.  Toc components, mediate
translocation (Toc75 is the
translocon); it is unclear how
preproteins are targeted to the
channel; Hsp70/Hsp40 may be
involved
 Hsp70 in both the IMS and the
stroma assist the threading of the
preprotein into the chloroplast
 an Hsp100 chaperone also called
ClpC (AAA ATPase) also binds
preproteins in the stroma
 Hsp70/chaperonin (Cpn60) may
assist folding/assembly of newly-
imported protein
 import into thylakoids (used for
respiration) uses the SRP pathway
10-9
Translocation into chloroplasts

11.  targeting of proteins is initiated
post-translationally by Pex5/7
proteins, which bind the peroxisomal
targeting signal (PTS)
 translocon not well defined;
possibility of vesicular budding?
 gated pore that is regulated by
membrane proteins?
 first organelle demonstrated to
import proteins without a PTS, by
virtue of assembly with other
proteins that contained a PTS
 various protein oligomers are
imported into peroxisomes
 antibodies with PTS, and 9 nm
gold particles could be imported
Other transport mechanisms likely involve
folded proteins, including the twin-arginine (Tat)
transport system of bacteria, and the cytoplasm-
to-vacuole targeting pathway of yeast
10-10
Translocation into peroxisomes

12.  nuclear localization signal (NLS) is typically highly basic; e.g., the SV40 large tumor
antigen (T ag) has the sequence PKKKRKV
 a/b1 importin hetero-dimer recognizes and binds the NLS (or b importin alone)
 b importin docks with NPC and mediates interaction with Ran (GDP form)
 directionality conferred by nature of guanine nucleotide bound to Ran
Ran binding protein (RanBP) is required for b importin binding to RanGDP; Ran
GTPase activating protein (RanGAP) and nucleotide-exchange factor (RCC) are
cytoplasmic and nuclear
 cytopl. RanGDP required for import; nuclear RanGTP required for release
 conversely, RanGTP binds substrate with NES in the export direction
 proteins to be imported can be in a native/near native form
10-12
Import into the nucleus

13.  some nuclear pore proteins (nucleoporins)
contain core FxFG repeats (yellow)
 b importin contains ‘heat’ repeats that bind the
FxFG repeats (Heat repeats 5, 6, 7 are shown in
red, green and blue)
 the FxFG repeats interdigitate in grooves formed
by the Heat repeats
 interaction of b importin with nucleoporins allows
transport across the nuclear pore complex
Core FxFG repeats found in nucleoporins.
Each repeat is separated by a ‘linker’ region:
Bayliss et al. (2000) Cell 102, 99-108.
10-14
Mechanism of import into nucleus

14. Oligosaccharide processing in Golgi
compartments

15. Protein Targeting in Golgi

16. Protein Secretion Pathway (E.R – Golgi and Vice Versa)

18. Thank You…