ne102 4/22 lecture: protein transport: how can proteins reach their final destination in a cell

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Last updated 5:03 PM on 5/6/26
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12 Terms

1
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what determines how proteins are efficiently directed to the specific organelle/cellular compartment where they’re needed?

  1. proteins include sequences of AAs that determine where they’re transported after translation

  2. all proteins translated in ribosomes, but some will remain cytosolic, while others can move to ER membrane to complete translation there; depends on specific sequence of AA in protein

  3. all proteins translated in ER are transported in the cell through vesicle transport

2
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<p>nuclear membrane + ER may have evolved from?</p>

nuclear membrane + ER may have evolved from?

prokaryotic cells

<p>prokaryotic cells</p>
3
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<p>intracellular membrane-enclosed organelles</p>

intracellular membrane-enclosed organelles

cytosol, nucleus, ER, golgi apparatus, lysosomes, endosomes, mitochondria, chloroplasts (plant cells), peroxisomes

<p>cytosol, nucleus, ER, golgi apparatus, lysosomes, endosomes, mitochondria, chloroplasts (plant cells), peroxisomes</p>
4
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how is it possible for organelles + membranes to function?

specialized proteins that are translated by ribosomes either at the level of ER or free in cytosol

5
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how can proteins make it to target organelle?

transport: each protein contains a short AA sequence that acts as a targeting signal, like a molecular pass that directs protein to correct organelle/membrane

6
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<p>3 ways of protein transport</p>

3 ways of protein transport

  1. through nuclear pores

  2. across membranes via protein translocators

  3. by vesicles

<ol><li><p>through nuclear pores</p></li><li><p>across membranes via protein translocators</p></li><li><p>by vesicles</p></li></ol><p></p>
7
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<p>signal sequences</p>

signal sequences

AA segment that acts as a target signal → directs protein to correct organelle/membrane; ex: DXXSLL internalization from plasma membrane, BACE LL/AA = bace accumulation at PM

<p>AA segment that acts as a target signal → directs protein to correct organelle/membrane; ex: DXXSLL internalization from plasma membrane, BACE LL/AA = bace accumulation at PM</p>
8
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<p>transport through nuclear pores</p>

transport through nuclear pores

pore = molecular pass that directs protein in/out of nucleus; mediated by nuclear receptors, karyopherins are importins + exportins

<p>pore = molecular pass that directs protein in/out of nucleus; mediated by nuclear receptors, karyopherins are importins + exportins</p>
9
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<p>outer nuclear membrane</p>

outer nuclear membrane

ts continuous w/ the ER, the most extensive membrane system in the cell

<p>ts continuous w/ the ER, the most extensive membrane system in the cell</p>
10
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<p>nuclear pore complex</p>

nuclear pore complex

a gate for the passage of proteins, made of nucleoporins

<p>a gate for the passage of proteins, made of nucleoporins</p>
11
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<p>pore transport process</p>

pore transport process

cargo + signal bind to receptor (karyopherin) → go through cytosolic fibrils → go through nuclear fibrils + basket → protein imported + delivered to nucleus

<p>cargo + signal bind to receptor (karyopherin) → go through cytosolic fibrils → go through nuclear fibrils + basket → protein imported + delivered to nucleus</p>
12
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<p>transport across membrane via protein translocators</p>

transport across membrane via protein translocators

ex: mitrochondrial translocators regulate import of cytosol-translated proteins that are essential for mitrochondrial function (TOMs + TIMs)

<p>ex: mitrochondrial translocators regulate import of cytosol-translated proteins that are essential for mitrochondrial function (TOMs + TIMs)</p>