Name 3 cleavable topogenic Signals
signal peptide
transit peptide
targetin peptide
Name 3 non-cleavable topogenic signals
signal anchor sequence
nuclear localization signal (NLS)
peroxisomal targeting signal 1 (PTS1)
Which peptides form the PTS1?
• PTS1 is usually the C-terminal tripeptide SKL or a close variant.
serine - lysine - leucine (SKL)
How is the dual targeting achieved on a molecular level?
• Dual targeting is achieved by a protein carrying ambiguous or overlapping targeting information, such as one signal being partially masked or one sequence being recognized by more than one import pathway
Net charge
For what can the saGFP system be used?
analyze protein targeting/localization in vivo, especially when attached to targeting signals to test import into organelles
Name the molecular architecture of Ffh
The molecular architecture of Ffh has three main parts: N domain, G domain, and M domain.
What are the functions of the different architectural parts?
Their functions are:
N domain binds the ribosome and FtsY,
G domain binds and hydrolyzes GTP
M domain binds the signal peptide
What is the targeting comple of the SRP pathway?
The SRP targeting complex is the SRP particle bound to the nascent chain and the ribosome, engaging the membrane receptor FtsY
What happened to the SRP in role of evolution?
Slide 20
In evolution, the SRP is highly conserved across bacteria, archaea, and eukaryotes.
What is the prerequisite for post-translational targeting factors in bacteria?
secretory protein
must stay soluble, non-folded or loosely folded
Which bacterial targeting factors compete for ribosome binding?
Slide 22, second slide
SecB and SRP compete for ribosome-associated targeting in bacteria
Which bacterial targetting factor can stop translation?
SRP
Which bacterial targetting factor binds substrate after translation is terminated?
Slide 18
SecB
What are OMP85 proteins and how are they characterized?
OMP85 proteins are outer-membrane protein insertion machines of the Omp85/BamA family.
They are characterized by a β-barrel membrane domain and conserved periplasmic POTRA domains.
Which Nups (nucleosporins) are most involved in the translocation process?
Slide 28
FG repeat nucleoporins
What is the maximum molecular weight and size for passive transport through NPC?
Slide 29
5 nm
Size of GFP
How are karyopherins classified?
importins and exportins and transportins
Name the 4 topogenic signals for nuclear translocation
Slide 31
cassical NLS,
basic PY-NLS
hydrophbic PY-NLS
NES
What is the basis of nuclear export and import? Role of NTF2
RanGTP/RanGDP gradient
NTF2 imports back into nuclesrplasm
Name the types of peroxisomal biogenesis
The main types of peroxisomal biogenesis are de novo formation from ER and growth/division of pre-existing peroxisomes
What is the most imprtant process for peroxisomal maturation?
Slide 34
The most important process for peroxisomal maturation is matrix protein import into existing peroxisomes, which drives maturation and growth
What is the receptor for PTS1 and the receptor for PTS2 in yeast?
Slide 36
In yeast, the receptor for PTS1 is Pex5, and the receptor for PTS2 is Pex7 with co receptor 18
Name the two main translocations proes of the TOC and TOM complex, what protein families do they belong to and how they differ?
Slide 38
The main translocation pores are Toc75 in chloroplasts and Tom40 in mitochondria
Toc75 belongs to the Omp85 family, while Tom40 belongs to the porin/VDAC-related outer-membrane translocase family.
Number of Beta barrels uneven - even
What is the topogenic signal for mitochondrial beta barrel proteins and where is it located?
Slide 44
The topogenic signal for mitochondrial beta-barrel proteins is a C-terminal β-signal located in the final strand region.
Is the canonical transprt to endosymbiosus organelles post- or co translational?
Canonical transport to endosymbiotic organelles is generally post-translational
Which translocation system do LHC proteins utilize?
LHC proteins use the chloroplast thylakoid insertion pathway, not the generic outer-envelope import route
What is the major difference between chloroplastidic SRP and all the other SRP systems?
The major difference between chloroplast SRP and other SRP systems is that chloroplast SRP is post-translational and uses cpSRP43/cpSRP54 without a 4.5S RNA in the bacterial-like way
No rna
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