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Applied Biology > Protein sorting I > Flashcards

Protein sorting I Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

why are post translational modifications necessary

A

regulate protein biological activity, location and interaction with other molecules

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2
Q

where do PTM occur

A

at distant amino acid sites

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3
Q

examples of PTM are

A

proteolysis, glycosylation, phosphorylation, ubiquitination

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4
Q

Proteolysis

A

is irreversible. Is used for protein sorting and regulating protein activity

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5
Q

glycosylation

A 
oligosaccharide chains (glycan) are added to proteins in the ER and Golgi.
it can happen in 2 ways: N-glycosylation or O glycosylation
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6
Q

N-glycosylation

A

occurs on asparagine residues

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7
Q

O-glycosylation

A

occurs on serine, threonine residues

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8
Q

what are the functions of glycosylation

A

correct folding of modified proteins and confer solubility, protect protein from proteolysis, may help cell adhesion, are used as surface signals

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9
Q

phosphorylation

A

occurs at Ser, Thr, Tyr residues. Is used to switch on/off proteins

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10
Q

ubiquitylation

A

ubiquitin is a small protein that can be covalently attached to other proteins on Lys residues.

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11
Q

mono ubiquitylation

A

histone regulation

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12
Q

multi-ubiquitylation

A

endocytosis

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13
Q

poly-ubiquitylation

A

proteosomal degradation

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14
Q

where do proteins go after synthesis

A

stay in the cytoplasm or be sorted to cell compartments

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15
Q

when can protein sorting occur

A

before or after synthesis

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16
Q

what are necessary for protein sorting

A

~localization signals: in the protein that must be sorted

~sorting receptor/translocator: guides protein to correct destination

17
Q

what are the 2 kinds of localization signals

A

~signal sequence: is a continuous stretch of AA

~ signal patch: separate AA motifs brought together when the protein folds

18
Q

note that

A

physical properties of he signal and location within a protein are more important than exact AA sequence

19
Q

proteins are sorted with 3 main methods

A

gated, transmembrane, vesicular transport

20
Q

what kind of transport is used to enter the nucleus

A

gated transport

21
Q

how do you enter the nucleus

A
  • through nuclear pores
  • small molecules can move by diffusion, macromolecules are transported by active diffusion
  • proteins can be transported fully folded
  • localization signal is not removed after sorting
22
Q

the nucleopore is

A

bidirectional , it imports histones, non histonic proteins, ribosomal proteins.
exports: mRNA and ribosomal units

23
Q

what molecules are actively transport through NPC

A

molecules >40kDa, is protein mediated, requires energy

24
Q

what molecules can freely diffuse through NPC

A

molecules <40kDa, and diameter<9nm

25
Q

NPC permeability declines with

A

age, due to deletion of some nucleoporin, and oxidative damage

26
Q

what are the 4 main substances involved in Nuclear transport

A
  • proteins of NPC
  • nuclear localisation signal, nuclear export signal
  • nuclear receptors (karyopherins)
  • monomeric Ran GTPase
27
Q

Nuclear localization signals

A

are one or two short sequences rich in basic amino acids (Lys Arg)

28
Q

nuclear export signals

A

sequences rich in hydrophobic AA - Leu

29
Q

what are the 2 kinds of nuclear receptors

A

importins and exportins

30
Q

nuclear transport requires energy when

A

when transporting in either direction

31
Q

where does energy for nuclear pore transport come from

A

Ran GTPase which has 2 states. Ran GAP (GTP activating protein) and Ran GEF (guanine exchange factor). They make a conformational gradient

32
Q

explain nuclear import

A
  • importin binds to cargo and NPC and transports it into nucleus
  • binding of RanGTP to importin causes cargo release
  • importin bound to RanGTP is transported back to cytosol
  • hydrolysis of GTP makes RanGDP dissociate from importin
33
Q

how does nuclear export work

A
  • in the nucleus, exportin binds both RanGTP and cargo and transports it to the cytosol
  • hydrolysis of GTP makes Ran GDP dissociate from exportin and cause cargo release
  • free exportin goes back to nucleus

Applied Biology (13 decks)

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